The Observer Corps’ Cold War bunker

The remains of a cold war ‘bunker’ are situated underground in the middle of a field, near the road from Witham to Hatfield Peverel.

A series of photos taken in 2021 by Peter Green will be included in the Photos section of this website, numbers  M3147 to M3165.

An anonymous report written on 06 June 1997 reads as follows:

This reference was kindly provided by Wayne Cocroft

The following account was also provided by Wayne Cocroft (
in 2022).

“It’s a Royal Observer Corps visual reporting post and underground monitoring post. From the photographs, I presume it’s the post described as Hatfield Peverel [in 1997].

There was another Observer Corps post in the area, first established at Hatfield Peverel in 1929 at TL 791 120. It was re-sited to its present position in November 1954, when presumably the structure on posts, known as an ‘Orlit B’, was built. It was one of 206 of this type built between about 1952 and 1955. Their function was to visually plot aircraft movements, this activity ceased by about 1965.

The underground structure now under consideration was a 3 or 4 person monitoring post. It was built in 1959, and its role was to plot the point of detonation of nuclear weapons, and plot the resulting spread of radioactive fallout. This role ceased in 1991, although this particular post was closed in 1968 as part of a rationalisation of the system. In total about 1500 underground monitoring posts were built in the UK.

It was post 4/K.4, indicating that it reported to the Group 4 headquarters at Colchester.

Wayne Cocroft FSA MCIfA
Senior Archaeological Investigator
Archaeological Investigation
National Specialist Services Department
Historic England
Brooklands, 24 Brooklands Avenue
Cambridge, CB2 8BU

A Video of the bunker, made in 2020, is at
Hatfield Peverel ROC & Orlit Post – Beyond the Point


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