Beacon Hill ringwork siege castle and Royal Observer Corps post


Heritage Category:
Scheduled Monument
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Ordnance survey map of Beacon Hill ringwork siege castle and Royal Observer Corps post
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The building or site itself may lie within the boundary of more than one authority.

North Yorkshire
Ryedale (District Authority)
National Grid Reference:
SE 79288 84439

Reasons for Designation

Ringworks are medieval fortifications built and occupied from the late Anglo-Saxon period to the later 12th century. They comprised a small defended area containing buildings which was surrounded or partly surrounded by a substantial ditch and a bank surmounted by a timber palisade or, rarely, a stone wall. Occasionally a more lightly defended embanked enclosure, the bailey, adjoined the ringwork. Ringworks acted as strongholds for military operations and in some cases as defended aristocratic or manorial settlements. They are rare nationally with only 200 recorded examples and less than 60 with baileys. As such, and as one of a limited number and very restricted range of Anglo-Saxon and Norman fortifications, ringworks are of particular significance to our understanding of the period.

Siege castles of all designs are nationally very rare. The earliest documented example in England was built by William Rufus in 1088 at Rochester in Kent. Some 20 examples are known to have been built during the anarchy of Stephen's reign in the mid 12th century, but after this their use appears to have fallen out of favour. Siege castles were not built to assault besieged castles, but to provide a base of operations to keep a check on the activities of the castle garrison. They were typically constructed in haste and placed anywhere between just out of bow shot (250m) and a couple of miles from the castle. Royal Observer Corps posts form a network of military sites largely established during the 1930s and 40s for tracking enemy aircraft. In 1952 this network was reorganised into territorially based groups and a new structure was introduced known as an Orlit Post. This was a rectangular box 3.1m by 2.03m formed from precast concrete panels, either sited on the ground or elevated 1.37m on concrete legs. Ministry of Defence records indicate that 413 of these posts were constructed in England. In the mid-1950s the Royal Observer Corps was given the role of monitoring nuclear fallout in the event of a nuclear attack. Between 1957 and 1965, 985 underground monitoring posts were constructed. These were formed by a buried reinforced concrete chamber 5.8m by 2.6m by 2.3m internally, accessed via a ladder down a 4.6m deep shaft from the surface. They were designed for a crew of four who might be required to remain inside the post for a week. In 1965 the Royal Observer Corps' role of visual aircraft observation was abandoned and the above ground posts were closed. Although new posts continued to be built into the 1970s, a large number of the early underground posts were decommissioned in 1968. The last posts were abandoned when the Royal Observer Corps was stood down in 1991 following the end of the Cold War. The 20th century reuse of Beacon Hill by the Royal Observer Corps provides an interesting parallel with the medieval siege castle, with the hill first being used to observe the besieged Pickering Castle, and then to keep a watch for 20th century `besiegers' during World War II and the Cold War. The 20th century remains therefore add to the already important Beacon Hill, a rare monument which provides an insight into the tactics of medieval warfare.


The monument includes buried and earthwork remains of a medieval ringwork siege castle constructed on a small natural hill to keep watch over Pickering Castle, which lies 550m to the east. It also includes the structural remains of at least two mid-20th century Royal Observer Corps posts. The monument forms a prominent mound, known as Beacon Hill, to the north west of the centre of Pickering. The Domesday Book of 1086 records that the manor of Pickering was held by the king, and an earthen motte and bailey castle, on the site of the existing stone castle, is thought to have been in existence by the time of Henry I in the early 12th century. The reign of the next monarch, Stephen (1135-1154), was marked by civil war and it is thought that the siege castle dates to an unrecorded siege of Pickering during this period. The first documentary records of Pickering Castle date from 1180-1187 and an inquiry into the state of repair of the castle in 1220 implies that Pickering had been besieged in 1216-1217 by supporters of Prince Louis of France. This suggests an alternative date for the siege castle. The earliest map on which the monument is shown is Jeffery's 1770 Map of Yorkshire which labels it as `Beacon'. The earthworks were described and a plan drawn in 1874 by GT Clark. It was mapped in greater detail by the Ordnance Survey in 1910 and was first identified as a siege castle two years later. By January 1937 a Royal Observer Corps aircraft observation post had been established on Beacon Hill. In December 1952 Air Ministry records noted the requirement for a prefabricated building, known as a ground level Orlit post, at Beacon Hill. By November 1961 this had been replaced by an underground monitoring post which was finally sold off by the Ministry of Defence after the Royal Observer Corps was stood down in September 1991. In form, the siege castle is best described as a ringwork. It was constructed by modifying the natural topography of the hill, cutting back its sides to create a steep sided mound topped by a low bank and surrounded by a ditch and outer bank. The top of the mound is roughly oval in plan, approximately 30m north-south and 25m east-west. A bank up to 0.7m high survives around part of this area, especially on the north, north east and south west sides. The south to south eastern section, mapped in 1910, has been disturbed by the construction of the various Royal Observer Corps posts sited on the mound. The top of the bank is nearly 4m above the foot of the mound which is up to 70m in diameter. It is surrounded by a largely infilled ditch which in 1874 was described as being up to 10m wide and not over 1.8m deep. This ditch survives as an earthwork on the south side of the mound and elsewhere as an infilled feature. Around the outer edge of the ditch there are the fragmentary remains of an outer bank which survives up to 0.4m high on the ENE and WSW sides and is marked by a break of slope around the rest of its circuit. Clarke suggested that the castle had an entrance on the south eastern side. Evidence for this has been obscured by 20th century constructions, but the mound is approached on this side by a possible trackway. This survives as a curving hollow which extends uphill from a field boundary ditch to the south east. On the south western side of the centre of the siege castle mound is a low rectangular mound 0.3m high, 15m by 10m, orientated north east to south west. This covers an underground Royal Observer Corps post built between 1958 and 1961. Protruding from the top of the mound to the north east is an access hatch, with an air vent to the south west and two metal monitoring probes between. Below is an underground concrete room 6m by 3m which would have held monitoring equipment and a staff of three people. On the southern lip of the top of the siege castle mound there is a small hut, 3m by 2m, of precast concrete panels. This is a ground level Orlit Observation Post which was erected after 1952 and was subsequently replaced by the larger underground post. Two parallel brick walls lie immediately to the east of this structure. These are interpreted as remains of an earlier observation post. A wooden fence extends around the Orlit and underground posts, defining the area originally under military control. This fence and all the other remains of Royal Observer Corps posts are included within the monument. A number of features are excluded from the scheduling: these are the post and wire fence which crosses the western side of the mound, the telegraph pole on the southern edge of the monument and the timber shed built in the ditch on the southern side of the mound; however, the ground beneath these features is included.

MAP EXTRACT The site of the monument is shown on the attached map extract. It includes a 2 metre boundary around the archaeological features, considered to be essential for the monument's support and preservation.


The contents of this record have been generated from a legacy data system.

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Books and journals
Dobinson, C, Twentieth Century Fortifications in England Volume 11 and appendices: The Cold War, (1998), 321
RCHME survey, RCHME, Beacon Hill Pickering SE 78 SE 14, (1988)


This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Digital, Culture, Media and Sport.

End of official listing

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