The Promontory Fort of Keston Common

( 124 ) THE PROMONTORY FORT ON KESTON COMMON. BY B. H. ST. J. O'NEIL. IN the hst drawn up by the Earthworks Committee of the Congress of Archaeological Societies, Group A is assigned to promontory forts, viz. " Fortresses partly inaccessible by reason of precipices, cliffs or water, defended in part only by artificial works." The writers of the Victoria County History in the chapter dealing with earthworks in Kent were unable to find any promontory forts and, as far as can be ascertained, none has hitherto been recorded in the County. On Keston Common there is an earthwork (Fig. I),1 which seems so far to have remained unexplained. Although well known to local archaeologists, in particular certainly to the late Mr. George Clinch, apparently the only reference to it in print is a passing remark in his Antiquarian Jottings (p. 136)—" the earthworks . . . facing the National Schools." It was, indeed, this sentence which directed the present writer's attention to the spot. The earthwork consists of a single bank and ditch of small proportions but readUy distinguishable from the cultivation banks or field boundaries, which exist further south as weU as on the nearby Hayes Common.2 A portion of it must have been destroyed during the working of the gravel pit immediately south and south-west of Caesar's Well. As it is, the end of the bank can be distinguished in section at the edge of the pit by the mauve tint of the disturbed gravel against the deep orange of undisturbed 1 The writer is indebted for help in planning this earthwork to Mr. R. S. Simms of H.M. Office of Works and Mr. J. B. Ward-Perkins, New College, Oxford. 2 Arch. Cant., XIII, p. 15. It is hoped to publish a revised plan of these as soon as completed. • * * EARTHWORK ON KESTON COMMON. THE PROMONTORY FORT ON KESTON COMMON. 125 ground beneath. The earthwork runs from the edge of this quarry in a dead straight hne westwards for 353 feet when there is a gap with corresponding causeway across the ditch. It proceeds thence, twice altering its course and descending the slope, into a smaU vaUey. A few feet only from the bottom of this vaUey it ceases abruptly ; there is no sign of any continuation up the other side of the valley, nor is there any suggestion that it once existed and has been leveUed. Consequently it must be assumed that the earthwork is complete except at its eastern extremity. Here it probably continued in the same straight line or turned shghtly to the north, descending the slope to the bottom of the vaUey and there terminated (as at the western end) at a spot due south of Caesar's WeU. The ground here has been much altered in recent years, but there is no indication within Holwood Park of any earthwork running up to the ramparts of Holwood Camp itself (" Caesar's Camp " on plan). The sections given with the plan on p. 126 and the photographs opposite indicate sufficiently the scale of the earthwork. West of the entrance it is shghtly higher in places, but nowhere is the crest of the bank more than six feet above the bottom of the ditch. Its alignment in three straight stretches is weU planned and calculated to leave no dead ground to the south. The entrance is simple and measures 28 feet from crest to crest of the ends of the ramparts, the actual flat passageway being 6 feet wide. The causeway over the ditch, however, is 16 feet wide ; it overlaps the end of the rampart at the eastern side. It may have been widened since the earthwork went out of use, for there are traces of a weU used vehicle-track within the camp approaching the entrance from the north-west. This single stretch of earthwork is unintelligible without consideration of the natural features of the district. The northern slopes of this region are intersected by a number of smaU vaUeys, which are noticeable for their copious supply of water. One at least of these within Holwood Park, 126 THE PROMONTORY FORT ON KESTON COMMON. 'JfAtffi" \ Hed/Afitld •-s c ,l„s -/'•»//^,A,!/5ll5SS Cam) \ \ I w; t. V\^ Foci 100 SECTIONS A ^ — t t ^ ^ ^ .3....^ PLAN OF EARTHWORK ON KESTON COMMON. THE PROMONTORY FORT ON KESTON COMMON. 127 which the writer has been privUeged to see, is stiU practicaUy in its natural state. The whole of the bottom of the valley is, for this part of England, extremely boggy. Although not dangerous, crossing needs care and takes time. The largest of these small vaUeys in the district is that which is now occupied by Caesar's Well and a series of ponds, two of which being on Keston Common are a favourite pleasure resort. It can readily be understood that before the making of the ponds by means of a series of dams and the sinking of the weU this vaUey also was extremely boggy ; it was, probably, quite impassable in winter. The bog must certainly have extended some distance south of the weU, which has served to drain the head of the vaUey, and also north of the third large pond. The other valley on the common contains only two smaU ponds. Between them the vaUey bottom is boggy and north of the larger pond this bog assumes considerable proportions, being in places nearly 40 feet wide. The slopes are very wet and the flat bottom is well-nigh impassable. The stream in this valley flows northwards and soon joins the river Ravensbourne, which rises at Caesar's WeU.1 South of the smaUer pond the valley bottom past the western end of the earthwork is now quite dry, but it is practicaUy certain that in prehistoric times the water level was generaUy higher, and there can be Uttle doubt that this also was then natural bog. The extent of this wet ground is marked on the plan by hatching. The areas which are stiU boggy are marked in solid lines, as are those outside the common, which must certamly have been bog until the advent of modern draining for agricultural purposes. The smaller area at the extreme south-west is marked with broken hnes. Thus there is a natural promontory comprising most of the common, defended on the two long sides by bog. The 1 The writer has recently heard from Mrs. Thompson, lately of Hayes Rectory, the most likely derivation of this name, viz. a combination of the old and new common names for a stream—yr afon (Celtic) and bourne (Saxon). 128 THE PROMONTORY FORT ON KESTON COMMON. only addition necessary in order to turn this to advantage as a camp in the Early Iron Age was a defensive earthwork at the base of the triangle. This was constructed in the manner aheady described. The proximity of this camp to the great Iron Age fortress in Holwood Park raises the question whether it is merely a subsidiary work, attached to the larger stronghold. As mentioned above (p. 125), however, there is no indication now of any actual connection between the two, and the promontory fort is certamly complete in itseU. In the absence of excavation the relative dates of the two works must remain uncertain.1 The promontory fort may be of earlier date than " Caesar's Camp ", which superseded it as the stronghold of the district, but on the other hand they may have been contemporary. In the latter case, although not actually joined together, the smaller camp would very Ukely have served as a pound for stock. The natural defences of bog and the single bank and ditch, even allowing for a paUsade, are not insurmountable objects for determined attackers,2 but they are certainly sufficient obstacles against cattle raising by roving bands of robbers. 1 No real help in this connection is supplied by Clinch's finds of flint implements in the area to the south of the earthwork, as recorded upon the O. S. map. 2 The extreme south-west corner of the camp is actually overlooked by higher ground, viz. the present road south of the Windmill, which is, also, the line of the prehistoric trackway to Hayes Common.