HOLWOOD ESTATE BROMLEY A REVIEW OF ARCHAEOLOGICAL INTEREST A R O U N D THE REDWOOD CENTRE Alison Dickens M I F A © Cambridge Archaeological Unit University of Cambridge March 2002 Report N o . 475 CONTENT LIST 1 Introduction 1 O u t l i n e 2 2 The Site 2 Geology 2 T o p o g r a p h y 2 3 Development Proposals and Current State of Understanding I n t r o d u c t i o n 2 The Redwood Proposal 3 The Stable Y a r d 3 4 Archaeological and Historical Background 3 I n t r o d u c t i o n 3 P a l a e o l i t h i c 450,000 -12,000 BC 4 M e s o l i t h i c 12,000 - 4,000 BC 4 N e o l i t h i c and B r o n z e A g e 4,000 - 600 BC 5 Iron A g e 600 BC - A D 43 5 Roman A D 43 - 410 6 Saxon 410 -1066 7 M e d i e v a l 1066 - 1 4 8 5 7 Post-medieval 1485 - Present S 5 The Topographic Survey 8 6 Fieldwork July 1999 and April 2000 8 N o r t h of t h e Redwood B u i l d i n g 9 S o u t h of F i v e I s l a n d s Pond 9 The c a r p a r k i m m e d i a t e l y n o r t h - w e s t of t h e h i l l f o r t 9 7 Subsequent Impacts on the Archaeological Record 9 Caesar's C a m p and I m m e d i a t e E n v i r o n s 9 8 Archaeological Potential and Strategies in and around the Redwood Building Footprint 11 L e g i s l a t i o n 11 P o t e n t i a l f o r A r c h a e o l o g i c a l S u r v i v a l 22 M i t i g a t i o n Strategies 23 9 Conclusions 13 The Redwood 23 The Stable Y a r d 24 10 References 14 LIST OF FIGURES (at back of report) Figure 1 Redwood and Stable Block Areas Showing K n o w n Archaeology Figure 2 A e r i a l Photographs S h o w i n g the C h a n g i n g A r e a of the Redwood Figure 3 Redwood Interior and Perimeter Showing O r i g i n a l G r o u n d Level Figure 4 Sections Across the Redwood Showing Present and Previous Ground Levels / 1 Introduction O u t l i n e 1.1 This archaeological review has been commissioned by Nicholson Estates. It examines the archaeological effects and opportunities arising from the development of land on the site of the Redwood Bui lding and Stable Yard areas, wi thin the H o l w o o d Estate at Keston, Bromley, N G R TQ41956 63488. 1.2 The modern day Estate, which includes a post-war industrial complex, is located within an area of archaeological significance as defined i n the London Borough of Bromley's Unitary Development Plan (UDP). In addit ion part of the Estate comprises part of a Scheduled Ancient Monument (SAM), Caesar's Camp (LO101), about 200m to the north- east of the Redwood Building. 1.3 The Cambridge Archaeological Unit (CAU) has been commissioned to: • Summarise the k n o w n archaeological record for the immediate vicinity of the Redwood Building and Stable Yard. • Assess the potent ia l for s igni f i cant i m p a c t u p o n the archaeological resource in that area. • Identify strategies to mitigate development impacts and satisfactorily accommodate and safeguard the future of any archaeological interests. 1.4 Several site visits were made i n 1997 and 1998 w h e n a previous development plan was under consideration. Subsequent visits were made during 1999, 2000, 2001 and 2002, inc luding carrying out two limited programmes of fieldwork outlined below (Knight 1999,2000). 1.5 Principal sources consulted for this research inc luded the Greater ^ L o n d o n Sites and Monuments Record ( G L S M R ) , Bromley Local History Library, the Piercy-Fox Archive at Bromley M u s e u m and those publ ished and unpubl i shed sources w h i c h c o u l d be accessed. Excluded are any records held by the West Kent Group and associated organisations. These records have been requested but are not to be • made available, a position reasserted in March 2001. 1.6 A detailed aerial photography survey and interpretative report was commissioned, as part of a study of the whole Estate, f rom A i r Photo Services L td . The relevant sections have been included in this report. The fu l l survey is included w i t h i n the report of the wider study (Dickens 1999: Appendix 3). 1.7 In late 2000, early 2001, the Engl ish Heritage Survey Section was commissioned to conduct a topographical survey of the whole Estate. Due to overgrown ground conditions, only the more open areas were surveyed i n late 2000 and an interim report produced (Barker 2000). Subsequently work began on the remainder of the programme but was interrupted by the outbreak of Foot & M o u t h i n A p r i l 2001 when English Heritage withdrew all its operatives from the field. In relation 1 to the Redwood, however, that area was included i n the 2000 survey and the results are considered here. 1.8 A topographical and geophysical survey of the southernmost area of the hillfort was commissioned from the Royal Commiss ion on the Historical Monuments of England (now the English Heritage Survey Section) and Geophysical Surveys of Bradford (GSB) respectively, as part of a previous application. This was conducted dur ing the early part of July 1997. The survey area lay wel l outside the area of current consideration and is only referred to for completeness. 2 The Site S t u d y A r e a 2.1 The area of pr imary consideration i n this report is that on and f > immediately around the Redwood Bui ld ing . Aspects of the wider estate w i l l be referred to when necessary to provide context. Geology 2.2 The 1:50,000 British Geological Survey map of the area (Sheet 271) indicates that four main geology types dominate the H o l w o o d area. The Redwood, indeed most of H o l w o o d Park, is located on an extensive area of sand and pebble Blackheath beds over ly ing the Woolwich beds of clays, sands and loams. The sequence is underlain by Thanet sand beds and Upper Chalk (white chalk w i t h bands of flint). T o p o g r a p h y 2.3 Height across the Estate varies considerably from about 165m A O D at the summit of H o l w o o d H i l l d o w n to about 120m A O D i n the north. H o l w o o d H i l l slopes steeply away to the south, rather less so to the north. The Redwood Building lies at about 160m above sea level. 2.4 Water courses and some ponds occur both w i t h i n and around the Estate. Immediately south of the Redwood is a large pond, the feature » called "Five Islands" on the Estate Plan of 1832. This may wel l be the remains of a clay pit dug to supply the nearby 14th century tile k i l n (see below). 3 Development Proposals and Current State of Understanding I n t r o d u c t i o n 3.1 Residential re-development is proposed on two parts of the site: • O n the site of the Redwood Building • In the Stable Yard 2 The Redwood is the main concern of this document, but the situation relating to the Stable Yard w i l l be summarised. The Redwood Proposal 3.2 The R e d w o o d B u i l d i n g is a large circular structure set w i t h i n woodland close to the top of H o l w o o d H i l l . It was built between 1979 and 1981 for the then site owners, Seismograph. 3.3 The proposal is to demolish the standing structure and replace it wi th a rotunda bui lding containing apartments. The footprint of the rotunda w o u l d occupy a slightly smaller area than that of the existing Redwood Bui lding. Below the new structure w i l l be provis ion for car parking, extending about 2m below the current ground level. 3.4 A s is described in detail below (4.8 - 4.12 and 7.5 - 7.8), a large ditched enclosure was revealed during construction of the Redwood. This was <^ investigated at the time by the West Kent Archaeological G r o u p however, as the results of the work remain unavailable, the overall extent and indeed precise location of the monument is unknown. 3.5 Location and characterisation of this monument is identif ied as an archaeological priority. 3.6 Archaeological investigation and mit igat ion i n this area w i l l be conducted under the requirements of Policy Planning Guidance Note 16 (PPG16) with any intrusive works approved by the English Heritage Archaeological Advisor for the area. The Stable Y a r d 3.7 Development in the Stable Yard w i l l involve demolition of the late 20th century office buildings with retention of the Stable Block itself. It has already been determined that bui lding in this area w i l l be pul led back off the toe of the re-established outer edge of the Caesar's C a m p f > hillfort. 3.8 Archaeological investigation and mitigation i n most of this area w i l l be conducted under the requirements of Policy Planning Guidance Note . 16 (PPG16) with any intrusive works approved by the English Heritage Archaeological Advisor for the area. A tiny proportion falls inside the S A M boundary. A n y activity in this area w i l l be subject to Scheduled Ancient Monument Consent. 4 Archaeological and Historical Background I n t r o d u c t i o n 4.1 The archaeology of the area around the Redwood Bui ld ing is initially considered i n chronological order. Each site or f ind spot wi th in the study area has been given a number, these relate to the concordance Table 4.1. These occur within the text i n bold and are shown on Figure 1. Not all periods are represented, but all are referred to as part of the 3 overall picture of the wider estate i n which this area sits. N B : a l l distance measurements are calculated from the centre of the Redwood Building 'r ing' . 4.2 A detailed consideration of the wider archaeological landscape can be found within the earlier study (Dickens 1999). Finds and Sites in the immediate vicinity of the Redwood Building REF. No. SMR No. Period Description N G R 1 IA Large ditched Iron Age enclosure found during construction of the Redwood (Grant 1979) T Q 419 634 2 IA Small Iron Age ditch found d u r i n g 1999 investigations (Knight 1999) T Q 42059 63547 3 IA Caesar's C a m p , Major Iron Age Hil l fort . T Q 421 638 4 070659 M D Medieval Tile K i l n partially excavated i n 1970s (Philp 1973) T Q 4200 6338 5 M D ? Five Islands Pond T Q 4201 6339 6 P M O l d H o l w o o d House, built 1642, precise location unknown. c. T Q 421 635 7 P M H o l w o o d House, built 1823. T Q 42059 63547 IA - Iron Age M D - Medieval P M - Post-medieval K A R - K e n t A r c h a e o l o g i c a l Review G L S M R - Greater London Sites & Monuments Record Table 4.1 Redwood Area: Site Gazetteer P a l a e o l i t h i c 450,000 -12,000 BC 4.3 N o Palaeolithic finds are recorded wi th in the wider Estate area, but one or two stray handaxe finds have been made 500m south of the Redwood. 4.4 Whilst the density of finds which can be dated to the Palaeolithic period maybe artificially low, due to problems of recognition and reporting, the probability of f inding anything other than the occasional stray find in the potential development area or the Wider Estate is very • low. M e s o l i t h i c 12,000 - 4,000 BC 4.5 Mesolithic finds are recorded from the Estate, particularly the "very heavy flint scatter" revealed dur ing the 1950s investigation of the hillfort. Further investigation revealed a similar floor on the other side of the valley on Keston Common (Piercy-Fox 1969: 189-90). Both finds lie between 400 and 500m north of the redwood. 4.6 These finds and others suggest that there may be further Mesolithic evidence i n the area, concentrated on the gravelly slopes of the Blackheath beds. The nature of the record of this period, wi th in the soil rather than protected beneath it, makes it very vulnerable to potential disturbance and damage compared to the rather more robust remains associated with later periods. N e o l i t h i c and B r o n z e A g e 4,000 - 600 BC 4.7 N o finds of this period are recorded within 1km of H o l w o o d House. I r o n A g e 600 BC - A D 43 Ref. Nos. 1,2, 3 4.8 Extensive archaeological evidence of the Iron A g e has long been known around Keston. 4.9 Immediately beneath the Redwood B u i l d i n g lies (1), a substantial ditched enclosure of the late Iron A g e discovered i n 1979 dur ing construction groundworks. Unfortunately no exact location was given for this i n the brief notes of its discovery (Grant 1979: 157; 1980: 45; Richardson 1981: 46). A document supplied by Brian Phi lp at the March 2001 Public Inquiry into an earlier development proposal, is the only publicly available notation of the f ind on a map but, by his own admission, was made from memory (Philp in evidence 2001). 4.10 The enclosure was described as "probably covering several acres", wi th wide deep ditches (Grant 1981: 143). A lso , according to the 1980 report, "(t)wo corners of a sub-rectangular enclosure and an entrance causeway were then located, together wi th a small amount of late Iron Age pottery" (Grant 1980: 45). M r Philp 's drawing, however, shows only one corner and it is not entirely clear whether Grant's 1980 note refers only to the enclosure itself or to another feature. The 1981 L o n d o n A r c h a e o l o g i s t round-up reports that "a ditch terminal suggests a possible entrance" (Richardson 1981: 46). Lack of detail aside, there are sufficient clues to indicate at least a ditched enclosure of significant scale. 4.11 The area occupied by the contractors d u r i n g construction of the Redwood Bui lding was plotted in the 1997 aerial photography survey but the extent of the archaeological investigations was not discernible (Dickens 1999: Appendix 3). 4.12 Given the evidence available the size, orientation and nature of the f ind cannot be determined, however two points were agreed by all parties; 1) The enclosure is of great significance given its apparent Iron Age date and proximity to the great Caesar's Camp Hil l fort . 2) Where impacted during construction work w i t h i n the Redwood footprint, the remains are likely to have been destroyed. 4.13 The recent w o r k at H o l w o o d (Knight 1999) revealed a hitherto unknown Iron Age ditch about l m wide and 0.35m deep (2). This was dated from small degraded sherds of pottery. It is not clear at this stage whether the feature relates to the Redwood enclosure, the main hillfort (below) or neither. 5 4.14 The most significant monument in the Wider Estate is the large hillfort wi thin the grounds of H o l w o o d House k n o w n variously as H o l w o o d or Caesar's Camp (3). This is considered i n some detail i n the earlier study (Dickens 1999). 4.15 The hillfort banks enclosed an area of about 16.8ha making it only slightly smaller than Maiden Castle i n Dorset and about one third the size of the Oldbury hillfort some 18km to the southeast (Hogg 1975). The hillfort is multivallate, wi th a double bank and ditch, the western side having the additional protection of a natural counterscarp bank. In places the outer bank survives at 17m wide by 2.50m high, the inner 7m wide by 1.20m high; the ditches 9.80m by 4.50m original depth and 6.7m by 2.50m (measurements taken from H o g g 1975: 159). The northern side formerly extended round to the northeast and south. Piercy-Fox reports that it is possible to trace the southern ramparts on the ground (1969:186). The recent surveys by English Heritage show that there are remains of the earthworks surviving immediately north of the kitchen garden (Barker 2000) and a series of l o w earthworks, which may be the remains of the southern ramparts, were noted i n the paddocks field to the east (Dickens 1999: Appendix 4). 4.16 Excavations i n the 1950s and 1960s showed that at least the inner rampart of the hillfort had been constructed i n three phases broadly during the middle and later Iron Age. 4.17 The recent f ieldwork at H o l w o o d included a trench i n the carpark north-west of the Stable Cour tyard , and two trenches inside the kitchen garden (Knight 1999, 2000). This al lowed a complete cross section of the outer ditch (at approximately TQ4211 6364) to be recorded and showed the middle bank r is ing to the east and the remains of a counterscarp bank rising to the west. It also re-established the southern line of the monument where it extends beyond the S A M area. This directly informed the relocation of the courtyard development proposed for the Stable Yard area. 4.18 The possibility that the H o l w o o d hillfort was part of a wider landscape extending beyond the ramparts and the land enclosed by them has long been a subject of discussion (Hasted 1797: 39-41; Roach Smith 1880: 3-4; C l i n c h 1889: 135-36; O ' N e i l 1933; Piercy-Fox 1969:186; Dickens 1999). Several apparently contemporary features have been recorded in the wider landscape and clearly the monument is intended to dominate the landscape around it, particularly to the north. Without better dating evidence for the Redwood enclosure, it is not yet clear how this fits into the wider scheme. R o m a n A D 43 - 410 4.19 Roman finds are recorded from the Estate, inc luding skeletons and pottery sherds. There is also a vague reference i n the G L S M R to "an important Romano-British site" investigated by the West Kent Group somewhere on the Estate in 1972/73 (Mynott 1972). N o other details and only an approximate location are recorded. 6 4.20 N o t h i n g Roman is recorded close to the R e d w o o d . The G L S M R reference to a terracotta lamp nearby has been shown to be incorrectly located (Dickens 1999:11). 4.21 To the west of the H o l w o o d Estate there is extensive evidence of Roman activity. This included a vi l la complex i n w h i c h indiv idua l buildings including a vi l la wi th evidence of a bath w i n g , and barn and corn dry ing oven have been identified, was excavated to the west (Philp 1991). Saxon 410 -1066 4.22 Although it is possible that the modern H o l w o o d Estate has its origins i n the Saxon period, no finds of the Saxon period are recorded from within the wider Estate. 4.23 To the west of H o l w o o d , evidence of Saxon settlement was found i n the vicinity of the Roman V i l l a excavations mentioned above, at Lower Warbank (GLSMR 070660). M e d i e v a l 1066 -1485 4.24 Al though medieval settlement must have been extensive around the general H o l w o o d and Keston areas, few individual items are recorded within the G L S M R . 4.25 Close to the southern side of the Redwood is an isolated tile k i l n (4), excavated in 1972 (Philp 1973a, 1982). Comparison w i t h other similar structures and the few pieces of pottery recovered indicated a medieval date, suggested by the excavator as being between about A D 1400 and 1480. Philp notes that a document of 1485 records the site of the k i l n as T y l e l a t h e f e l d and that the means of tile production, clay, wood and water were available locally in good supply (1982: 149). It has previously been postulated that 'Five Islands P o n d ' may be the remains of a clay pit for the k i ln , and it is interesting to note that the recent E H survey indicated an area extending to the south of the present pond which seems to indicate that it was original ly much larger (Barker 2001: Figure 3). 4.26 A possible context for the k i l n is provided by Piercy-Fox's reference to "an interesting group of [medieval] tenements just outside the southern entrance to Caesar's C a m p " (1955: 96). Unfortunately no further information or a source is given for the statement. 4.27 The recent survey by English Heritage i n the Paddock Fie ld does appear to have found evidence of a small farm or settlement, hitherto unknown. L o w earthworks could represent a series of enclosures wi th an associated bui lding, pond and wel l . Al though a f i rm date cannot be determined at this stage the R C H M E thinks it most l ike ly that it predates the estate improvements of the late eighteenth century. "In this case the prox imi ty of a medieval tile k i l n should not be overlooked" (Dickens 1999: Appendix 4). 7 Post-medieval 1485 - Present 4.28 The principal post-medieval structure wi th in the development area is H o l w o o d House itself (7), its antecedents and any ancillary buildings associated w i t h its different phases. The original house was built around 1642, but its precise location is not k n o w n (Approximate location at (6)). After several owners the Estate was purchased by Wi l l i am Pitt the Younger in 1785. H e made only minor changes to the house (Watts 1982), but had a major effect on the surrounding park, including the Iron Age hillfort (see below). In 1823 the new owner, John W a r d , demolished the house and had a new one built i n the Georgian style. W i t h Victorian additions this is the house that stands today. 5 The Topographic Survey 5.1 A detailed topographic Survey was undertaken i n October 2000 by a team from English Heritage, formerly the R C H M survey team (Barker 2001). Due to thick ground cover the survey was largely l imited to the more open areas. The results as they relate to this report are summarised below. 5.2 Framing Five Islands Pond on all but its northern side was a scarp up to 1.60m high. Al though this might s imply indicate that the pond had been larger, it may have originated as a clay pit associated w i t h the k i l n to the east. Smaller scarps around the pond may represent spoil from the extraction process. 5.3 A number of scarps were picked up around the Redwood, however these are entirely modern resulting from the construction phase. 5.4 North of the Stable yard area several earthworks were recorded which almost certainly relate (in part or whole) to Caesar's C a m p . One of these lies immediately north of the kitchen gardens and greenhouses. 6 F ie ldwork July 1999 and A p r i l 2000 6.1 , T w o l imi ted programmes of f i e ldwork were commiss ioned to determine whether there were l ikely to be significant archaeological constraints on specific areas of the estate: • North of the Redwood Building • South of "Five Islands" pond • The carpark immediately north-west of the hillfort. • The Stable Yard area 6.2 The work is ful ly reported separately, but the pertinent points are summarised here (Knight 1999, 2000). 8 N o r t h of t h e Redwood B u i l d i n g 6.3 Ecological constraints meant that the area available for trenching was limited, but six trenches were placed i n the pathways around the zone. N o archaeological features were found. 6.4 In the area east of the Redwood, wi th in the zone identified i n the A P survey as disturbed during its construction, two trenches were dug. A single small ditch was found, dated by pottery to the Iron Age (2). 6.5 N o evidence was found relating to the Iron Age enclosure reported i n 1979 (see above). The shallow ditch that was uncovered was only l m wide and 0.35m deep S o u t h of F i v e I s l a n d s Pond 6.6 Three trenches were dug, again their location being agreed so as to avoid protected trees. 6.7 N o archaeology was found other than three post-medieval post holes close to the drive. Some evidence was found i n the trench closest to the medieval tile k i l n which may relate to previous archaeological investigations. There were also a number of deep boreholes, presumably related to use of the site by Seismograph between 1953 and 1990. The c a r p a r k i m m e d i a t e l y n o r t h - w e s t of t h e h i l l f o r t 6.8 Although the carpark trench came no closer to the S A M boundary than 5m, the ful l width of the outer ditch and part of banks on the inner and outer edges were exposed. Careful stepping al lowed the ful l ditch sequence to be examined and a series of environmental and pollen samples to be taken. 6.9 The location now established for the outer ditch confirms the accuracy ^ of Milne 's plot. The sequence appeared very similar to that recorded by Piercy-Fox i n her excavations. 7 , Subsequent Impacts on the Archaeological Record Caesar '$ C a m p and I m m e d i a t e E n v i r o n s 7.1 Dur ing its 2000 year history the H o l w o o d hillfort and the surrounding area has been subject to various activities which w i l l have had a greater or lesser impact upon the archaeological record. Some of these can be quantified and considered in detail, others can be surmised, whilst a small group are k n o w n to have taken place but are not at present known in any detail. 7.2 Land use over the hillfort and its environs was not recorded i n any detail before the seventeenth century. The late medieval tile k i l n (4) suggests that localised clay extraction was carried out, but this cannot be precisely located. Topographical survey suggests, however, that 9 Five Islands Pond (5) may have its origins as a much larger feature e.g. a clay pit. 7.3 From the m i d seventeenth century the hillfort lay wi th in the parkland of H o l w o o d House. Documents refer to land, pasture and woodland (BL A d d . M s 5487 f.49). In the eighteenth century the estate seems to have changed hands frequently. One owner, Robert Burrows , "grubbed and converted considerable woods into beautiful pasture and pieces of water and planted those ornamental shrubbery's w h i c h rendered it so justly admired" (Copper P l a t e M a g a z i n e V o l . 2). However it was not unti l the ownership of W i l l i a m Pitt the younger between 1785 and 1802 that the major phase of landscape alteration at H o l w o o d took place, though by that time the southernmost part of the rampart had already been levelled. 7.4 A r o u n d 1802 the estate was sold to John W a r d who carried out his o w n extensive alterations. The house was demolished and a new one, ^ designed by Decimus Burton, was built rather closer to the hillfort. The garden and stable block occupy approximately the area of the putative southern entrance. Clearly this work w i l l have damaged the archaeology to an extent but investigation i n that area shows that significant remains do survive. 7.5 In modern times, the degree of potential impact on the archaeological record has increased. Bui lding work around the stable block and the construction of the Redwood Bui lding w i l l have had a major impact, the former on the possible southern entrance, the latter on the late Iron Age enclosure (1) discovered during the bui lding works (Grant 1980). A s discussed below, however, it is possible that some of the enclosure may survive, even wi th in the Redwood circle. The reports of the Redwood works are very l imited. The references are reproduced below: 7.6 For 1978 the West Kent Archaeological Group reported that: "During 1979 a massive building programme has been undertaken by Seismograph Ltd. and we are excavating trial trenches over 15 acres ahead of this development". (Grant 1979:157) 7.7 For 1979: "... on a major office-construction within Holwood Park close to the Iron Age hillfort and the medieval tile kiln. The contractors stripped a large area and revealed one side of an unknown Iron Age enclosure. Rapid work on the edge of the contract area revealed a single large ditch. Some 3m deep and more than 4m wide. Two corners of a sub-rectangular enclosure and an entrance causeway were then located, together with a small amount of late Iron Age pottery". (Grant 1980: 45; Richardson 1981: 46) 7.8 For 1979/1980: 10 "During trenching for foundations for a large new office block near the Iron Age hillfort at Holwood House, Keston, an entirely new late Iron Age site was located. This was a ditched enclosure probably covering several acres. The ditch, about 5m deep and 3m wide could be defensive in character but does not seem to relate directly to the nearby Iron Age hillfort". (Grant 1981:143) 7.9 The 1987 storms had a particularly damaging effect on parts of the H o l w o o d Estate wi th it being reported that some 2000 trees were lost in the area overnight. This w i l l certainly have had a detrimental effect on sub-surface remains particularly as trees were uprooted. Fragile remains such as those from the Mesolithic period for example are the most likely to have been damaged by this event. Some work was done in relation to this, but again it is not clear what or where: 7.10 Between 1987 and 1989: "Following the 1987 hurricane the group undertook extensive surveys of uprooted trees especially in the Keston - Hayes area. This revealed further information on the important Iron Age site at Holwood and, with the kind permission of Seismograph Ltd., trial excavations then took place." (Grant 1989:106) 7.11 In 1990: "Archaeological work has continued at Holwood, Keston, with the kind permission of Seismograph Ltd. proving the importance of both the Iron Age and Roman sites, which covered an extensive area". Qohnstone 1990:19) 7.12 In summary dur ing the recorded history of the monument the most severe damage to the archaeological record is l ike ly to have been caused by the various phases of house and landscape 'improvement', particularly that of Pitt, activity associated w i t h the ownership of Seismograph Ltd . , significantly construction works , landscaping and tree planting as wel l as storm damage and the various archaeological interventions of the later twentieth century. 8 Archaeological Potential and Strategies in and around the Redwood Building Footprint L e g i s l a t i o n 8.1 Development work i n this area lies outside the zone governed by Scheduled Ancient Monument legislation. However, it is subject to the requirements of Planning Policy Guidance Note 16 (PPG16) and the L o n d o n Borough of Bromley's Uni tary Development P lan (March 11 1994). The latter (Policy E9 'Ancient Monuments and Archaeology) states that: (i) suitable designs, land uses and management strategies are achieved to safeguard archaeological sites and ancient monuments and that the most important remains and their settings are permanently preserved; and (ii) provision is made at sites of potential archaeological importance for an appropriate level of investigation to be undertaken by a recognised archaeological organisation before any development commences. ....It is important to increase public awareness of the historical and archaeological heritage of the Borough and to encourage its effective management as an educational and recreational resource. The Council will promote the conservation, protection and enhancement of ancient monuments and presentation to the public... P o t e n t i a l f o r A r c h a e o l o g i c a l S u r v i v a l 8.2 Only one significant archaeological f ind is k n o w n from this area, the late Iron Age enclosure and any associated features (1) found during construction of the Redwood. 8.3 A l t h o u g h , as described above, the location of the feature is not precisely known, the general area in which it lies has been narrowed d o w n . The brief descriptions available suggest that a significant proportion of its circuit was uncovered (though how much was dug is unknown) and its location makes it highly probable that it was at least part ial ly destroyed d u r i n g construction of the R e d w o o d itself. Without details of the 1979/80 works it is difficult to predict its present condition in detail. 8.4 A s part of this review a careful study has been made of aerial photographs of the Redwood site taken i n 1971 (prior to construction), 1981 (during the construction programme) and 1991 (with the bui lding complete). Comparison of these suggest that it may be possible to locate the ditched enclosure immediately outside the R e d w o o d footprint and, less certainly, that there may be some survival inside the central part of the ' r ing ' (Figure 2). Great caution must be taken i n relation to the second part of this statement. The photographs are three captured moments over twenty years, but they do seem to indicate that, other than for construction of the electricity substation and landscaping, the ground i n the central ' i s land' of the Redwood may not have been significantly disturbed. Indeed the 'eye of faith' identifies several trees which seem to appear on all three photographs. In 1971 the area that w o u l d become the ' is land' was largely taken up w i t h new coniferous planting extending to the north-west w i t h the eastern third clear mown. A handful of larger trees appear to have been retained within the plantation area, and it is some of these which may still exist, along with one or two of the plantation trees. 12 8.5 Study of the area from survey data and on site supports the impression gained from the aerial photographs (Figures 3 & 4). It is l ikely that the central i s land, other than where impacted by the sub station, represents a remnant piece of original ground surface and clear that the Redwood itself was built below the prevail ing level. Outside the ' r ing ' , particularly on the South and West the original ground level stands up to 1.90m above the construction level of the Redwood Building. This lessens the chance for archaeological survival below the structure itself, but increases it for the undisturbed areas around the perimeter of the building. M i t i g a t i o n Strategies 8.6 A s referred to above all works on the site w i l l be subject to and follow the guidelines set down in PPG16 and the Unitary Development Plan. 8.7 This w i l l require evaluation of any areas to be impacted, details of which w i l l be agreed i n advance and approved by Bromley and the Archaeological Advisor for the district as has been the case throughout the various stages of this project. 8.8 Final determination of a mitigation policy w i l l follow from these initial investigations but may include: • Mitigation by record (excavation) • Mitigation by preservation • A combination of the two 9 Conclusions 9.1 The H o l w o o d Estate sits at the heart of an important and varied archaeological landscape. 9.2 A l t h o u g h much of this resource has been adversely impacted by various activities over the centuries, much of it survives i n good condition both above and below ground. 9.3 , The proposed developments are w i t h i n areas of important archaeology, but the fol lowing steps w i l l be taken to ensure that no further damage occurs. These can be summarised as follows: The Redwood 9.4 Detailed evaluation w i l l be carried out, mainly i n the area immediately outside the bui lding, i n an attempt to locate the Iron A g e enclosure ditch and determine to what extent it has already been damaged. It has been accepted (see 4.12) that where impacted dur ing construction work wi th in the redwood footprint, archaeological remains are l ikely to have been destroyed. 9.5 Based on these results an appropriate mitigation strategy w i l l be devised in consultation with both advisory and statutory bodies. 13 The Stable Y a r d 9.6 Work has already been carried out to re-establish the outer l imit of the Caesar's Camp hillfort, and has done so successfully. 9.7 A n approved plan is i n place for careful monitoring of demolition i n this area relating to both the S A M and P P G 16 areas. 9.8 The plans for this area have been designed so as to p u l l all elements of the proposed development back from the 'toe' of the monument. These plans are considered appropriate by both the Local Authori ty and English Heritage. 10 References Barker , L . 2001 The H o l w o o d E s t a t e B r o m l e y , Greater L o n d o n : Phase 1 S u r v e y I n t e r i m R e p o r t English Heritage Cl inch, G . 1889 A n t i q u a r i a n J o t t i n g s R e l a t i n g T o B r o m l e y , H a y e s , K e s t o n A n d West W i c k h a m I n K e n t : 135-138 Dickens A . 1999 H o l z v o o d E s t a t e B r o m l e y : A Review of t h e A r c h a e o l o g i c a l I n t e r e s t i n t h e H o l w o o d E s t a t e C A U Report N o . 331 Grant, P. 1979 West Kent Archaeological Group K e n t A r c h a e o l o g i c a l Review N o . 57: 157 Grant, P. 1980 West Kent Archaeological Group K e n t A r c h a e o l o g i c a l Review N o . 62: 45 Grant, P. 1981 West Kent Archaeological Group K e n t A r c h a e o l o g i c a l Review N o . 66:143 Grant, P. 1989 West Kent Archaeological Group K e n t A r c h a e o l o g i c a l Review N o . 95:106 Hasted, E. 1797 The H i s t o r y and T o p o g r a p h i c a l S u r v e y o f t h e C o u n t y of K e n t V o l . II: 37-39 Hogg, A . H . A . 1975 H i l l - F o r t s of B r i t a i n Hart-Davis, MacGibbon, L o n d o n Johnston, L . 1990 Bromley and West Kent Archaeological Group K e n t A r c h a e o l o g i c a l Review 101:19 Knight, M . 1999 A r c h a e o l o g i c a l I n v e s t i g a t i o n s at t h e H o l w o o d E s t a t e , B r o m l e y : A n I n t e r i m S t a t e m e n t C A U Report N o . 333 Knight, M . 2000 A r c h a e o l o g i c a l I n v e s t i g a t i o n s at t h e H o l w o o d E s t a t e , B r o m l e y : M a y 2 0 0 0 C A U Report N o . 372 Mynott, E. 1972 West Kent K e n t A r c h a e o l o g i c a l Review N o . 29: 257 O ' N e i l , B. H . St. J 1933 The Promontory Fort on Keston C o m m o n A r c h a e o l o g i a C a n t i a n a 45: 124-128 Philp, B. 1973 The Medieval T i le -Ki ln at Keston K e n t A r c h a e o l o g i c a l Review N o . 33: 79-82 Phi lp , B. 1982 The Medieval T i l e - K i l n at H o l w o o d , Keston K e n t A r c h a e o l o g i c a l Review N o . 67: 146-149 14 Philp, B. 1991 The R o m a n V i l l a S i t e at K e s t o n , K e n t : F i r s t R e p o r t ( E x c a v a t i o n s 1968 - 1 9 7 8 ) CIB, Dover Piercy- Fox, N . 1955 Warbank, Keston: A Romano-British Site A r c h a e o l o g i a C a n t i a n a V o l . 69: 96-116 Piercy-Fox, N . 1969 Caesar's C a m p , Keston A r c h a e o l o g i a C a n t i a n a V o l 84: 185-199 Richardson, B. (ed.) 1981 Excavation Round-up 1980: H o l w o o d Park, Keston The L o n d o n A r c h a e o l o g i s t V o l . 4.1: 46 Roach Smith, C . 1880 H o l w o o d and Keston A r c h a e o l o g i a C a n t i a n a V o l 13: 1-7 Watts, M . C . 1982 The H o l w o o d E s t a t e , K e s t o n Seismograph 15 Figure 1 Redwood and Stable Block Areas Showing known Archaeology in the Vicinity (The Redwood Enclosure Ditch is Taken from a Sketch Produced by Brian Philp at the 2001 Public Inquiry) Central Island from the South Figure 4 Sections Across the Redwood Showing Present and Previous Ground Levels