Royal Observer Corps (ROC) Orlit Type B visual observation post and an ROC underground monitoring station, 604m west-north-west of Lodge Farm

This site comprises a Royal Observer Corps (ROC) Orlit Type B visual observation post, built between 1952 and 1956, and an ROC underground nuclear monitoring post, constructed in 1968, situated 604 metres west-north-west of Lodge Farm.

The Orlit Type B visual observation post is constructed from prefabricated concrete panels with a concrete slab roof over the former equipment store and shelter on the west side; the former observation room is unroofed. The rectangular structure is aligned east to west and raised 1.82 metres above ground level on four concrete legs. It follows a standard design by Messrs Orlit Ltd of Colnbrook, Buckinghamshire. A doorway, now lacking a door, is located at the west end of the south side and is accessed by a concrete ladder with steel rungs and a steel handrail. The doorway leads into the former equipment store and shelter at the west end. Adjoining it to the east, and divided by a concrete partition wall, is the unroofed former operation room. No significant fixtures or fittings remain.

The ROC underground nuclear monitoring post is of reinforced concrete with a compacted earth covering and is aligned north-east to south-west. It follows the standard Cold War design and consists of a rectangular, reinforced-concrete bunker concealed beneath a low, elongated earthen mound. A raised concrete entrance hatch is situated at the north-east end of the mound and a smaller raised concrete air vent at the south-west end; between them are two metal monitoring probes. A mushroom-shaped mounting for the Ground Zero Indicator is placed on top of the air vent adjacent to the entrance hatch. The access hatch has a counterweighted steel door that is now welded shut, leading to a 4.6-metre-deep shaft containing a single metal ladder. At the bottom of the shaft is a small chamber containing a store cupboard and a chemical toilet, with a further door leading to the monitoring room, which measures approximately 4.5 metres by 2.25 metres.