MMO459 - Possible prehistoric hillfort or 19th Century reservoir on Birchcleave (Monument)

An earthwork consisting of a wide flat-bottomed ditch cut into the slope of the hill with an external bank. A reservoir built for John Knight after the 1820s, with possible origins as a prehistoric hillfort.

SS 7803 3915 - EARTHWORK ON BIRCHCLEAVE Recent maps show a pear shaped enclosure defined by hedge banks within an area of regular rectangular fields. In 1887 [1] and 1891 [2] the area of the enclosure is shown as rough grassland when the surrounding area had been improved. However, by 1903 [4] the interior had also been improved. Air photographs from 1947 [3] show earthworks defining the perimeter of the enclosure. The earthwork lies on the summit of a gentle hill to the north of the River Barle, east of Birchcleave Wood, at 375 metres OD and centred on SS 7803 3915. It measures 250 metres by 150 metres. The earthwork predates two phases of field banks, the first of which fossilises its perimeter; the second of which links the site with the surrounding field systems. This stratigraphy is visible at the eastern end of the earthwork where two mounds survive as remnants of the first field bank phase before it was extended to meet Winstitchen lane during the second phase when one of the mounds was cut by the later field bank. Within the northeastern edge of the earthwork, in the ditch, there is an area of marsh. This was shown as a pond in 1887 [1], and was probably constructed to exploit a natural spring. The earthwork consists of a wide, flat-bottomed ditch cut into the slope of the hill with an external bank which the first enclosure phase has fossilised. The ditch is between 0.4 metres and 0.8 metres deep and averages 20 metres wide. In the northeastern corner of the earthwork, around the pond, the ditch is wider. This is probably due to natural erosion. To the north and west there are beech tree-lined mounds of around 1.2 metres high which form the residual external bank of the earthwork. The fragmentary nature of this bank is due to differential improvement in the surrounding fields and to surface quarrying for slate. This is shown by the position of the field banks in 1889 [2] which enclosed the central area to the north where the bank is largely missing. At the western end of the site, close to a gate, is a causeway. It is impossible to know whether this feature is contemporaneous with the earthwork or whether it is associated with the later quarrying activity or access to the field. On the field bank forming the south side of the enclosure, directly to the west of some modern sheep pens, there is the remains of a field bank emerging from the hedge which is shown in 1889 [2] and 1903 [4]. Within the earthwork the surface is covered with the amorphous scarps including a U-shaped hollow to the north. The interior is very uneven although it reaches a summit in the centre with excellent panoramic views over the surrounding area. Despite the shape and its topographic qualities the site does not appear to be prehistoric. It is not shown in 1809 [5] although at the time the area lay in the proximity of two roads. Also the scarps on the southeastern edge seem too sharp and the ditch too levelled and wide for there to have been any great amount of silting up over time as would surely have been the case, particulary with the later improvement of the land. Local information [6] suggests that the area is known as "Reservoir Field". While this name could apply to the pond rather than the entire field, it is feasible that the earthworks once contained water. The water from the spring as well as rain water could have been collected inside the ditch and retained by the enclosing dam. Water could then have been stored adequately until required. The water may have been used either to supply the people of Simonsbath, or for agriculture and for powering machinery. Despite the poximity of the River Barle, a hilltop reservior would have been potentially very useful for this. The dearth of nearby leats suggests that either the project was never completed, or that pipes could have been used to transport the water away. The site appears to be a creation of John Knight who purchased the land in 1820 [7]. Despite the legislation for enclosure in Exmoor in 1815, the Inclosure Map of 1819, [7] only shows lowland enclosure. Therefore one can assume that the area was still unenclosed in 1821. The peak of improvement activity by John Knight was during the 1820s and 1830s after which he concentrated on areas further from Simonsbath [7]. During this early improvement phase, work was concentrated on the south facing slopes north of the River Barle between Cornham and Honeymeads [8] - an area which includes this site. Therefore it appears that the earthwork was built and subsequently enclosed within John Knight's time. This short period of use suggests either that the project failed or was abandoned. This is supported by the fact that very little appears to be known about the site. Surveyed at 1:2500 scale, 26th October 1994. [9] The pear shaped enclosure on a hilltop east of Simonsbath village has previously been described as post medieval in date, based mainly on its unusual morphology (a shallow internal ditch and broad falt-topped remnant outer bank). However recent work on Exmoor's moorlands by the Exmoor Mires Project has developed our understanding of the work of John and Frederic Knight on Exmoor in the 1800s, and it now seems less likely that the enclosure can be ascribed to this period. It therefore now seems more probable that the enclosure is prehistoric in date and is better interpreted as one of the 'chain' of hillforts along the Barle valley. A detailed survey of the enclosure would help to determine this as well as to better understand its unusual form and morphology. [14] An account book written for John Knight in 1819 includes references to a reservoir at Birchcleave. On July 6th, there is reference to "Trigging [?] out Birch Cleve Reservoir". On the 7th March 1820, 4283 yards of soil were moved and 708 solid yards puddled. [15] It is possible that the larger earthwork feature on the site is a mutilated or unfinished hillfort, within which is the 19th Century reservoir. The site is right for this type of feature and it would form part of a chain running up from Oldberry (MSO9326). There is an obvious reservoir on site, but it is not clear whether this is what source [15] is referring to, and it is not clear whether it is ground fed or if the water is piped in. [16] This record was enhanced as part of the National Record of the Historic Environment to Exmoor National Park Historic Environment Record data transfer project. [17] An impact appraisal of the site of a proposal communications mast at SS7835739545 to the east concluded that no evidence of significant archaeological remains was encountered on the site, and the erection of the proposed telecommunications mast would have minimal or no impact on non-designated and designated heritage assets in the local area. [18] An examination of Lidar data suggests that this was a carefully engineered circuit reservoir or faux moat to provide a water supply which was also intended to be an aesthetically pleasing landscape feature. The attempt to create a reservoir was partly or wholly abandoned. It is thought likely that the field system and enclosure were constructed contemporaneously. There appears to be an entrance to the south where two field boundaries curve into the enclosure. This entrance is now partially closed by an e-w boundary. The outer enclosure boundary is at a near constant elevation and has been built up on the east side to cross two natural gullies. The water supply was from higher ground to the north- east, water would be held between an inner cutting and the enclosure boundary bank. Modelling shows an image of the encircling water at the 378.2m contour. The distance would match the 708 yards mentioned in the account book of 1819. A later stage of development appears to be the creation of earthen tank reservoirs also not completed. [19] The heritage asset was assessed for inclusion on the Exmoor Local Heritage List in February 2024. It was noted that it has a distinctive shape and is fairly unique as a water feature on Exmoor and rare if a modified prehistoric enclosure. It's evidential value is high as probably only greater survey and archaeological excavation will clarify the origin and purpose of the site. It was decided to add the asset to the Local Heritage List. [20]