June 19, 2010By

The Royal Observer Corps (ROC) was a civil defence organisation operating in the United Kingdom between 29 October 1925 and 31 December 1995, when the Corps’ civilian volunteers were stood down.Comprised mainly of civilian spare-time volunteers, ROC personnel wore a Royal Air Force (RAF) style uniform and latterly came under the administrative control of RAF Strike Command and the operational control of the Home Office.

Originally there were some 200 observation posts throughout the country and their role was to provide visual detection, identification, tracking and reporting of aircraft over Great Britain during the World Wars. Early Observation Posts were often crude and un-fortified but during the war many were rebuilt from brick and had sandbag defences.

On 12 May 1945 when the German Luftwaffe had ceased combat operations the ROC stood down, however it wasn’t long before the threat of Cold War arose and the ROC were reinstated.

In 1957, the United Kingdom Warning and Monitoring Organisation (UKWMO) was established under Home Office control to provide essential information about impending nuclear attacks to both civilian and military authorities.So that the ROC could work with the new type of threat the old monitoring posts were replaced with something that had protection from nuclear blasts.

Between 1958 and 1968 a countrywide building programme resulted in a network of 1,563 underground monitoring posts, approximately eight miles apart, distributed throughout England, Scotland, Wales and Northern Ireland, at an estimated cost of almost £5,000 each.The bunkers were built by digging a 25 feet deep hole, placing a reinforced concrete bunker in the hole and then burying it under compacted soil.A single hatch to the surface was the only entrance/exit with a 20 ft vertical ladder that lead to an underground chamber 7ft x 16ft x 7ft high.Posts were typically grouped together in threes or sometimes four, to form a cluster. One post in each cluster was a master post and could communicate directly back to ROC Control using a Tele-Talk device connected to ROC Group HQ and the Carrier Warning Receiver.

No telephones were provided. Each ROC Post was manned by 2 to 3 people who ate and slept in very primitive conditions as there was no electricity or running water in the bunkers, toilet facilities were by way of an Elsan Chemical Toilet located at one end of the bunker.

The ROC Post had a variety of external equipment fitted as standard:Bomb Power Indicator (BPI) – This would register the pressure wave from a nuclear explosion passing over it and the results were read on a dial inside the ROC Post.


Ground Zero Indicator (GZI)– Basically a crude pinhole camera that could ‘photograph’ the fireball of a nuclear explosion.
Radiac Meter – Used to count radioactive particles
Fixed Survey Meter (FSM)– Replaced the Radiac Meters and used to detect nuclear fallout. (The FSM could be safely operated without leaving the bunker)
Cross section of a ROC Post


After bomb a detonation, the direction, elevation and spot size of the fireball and reading of the pressure wave on the BPI would be passed to ROC Group HQ using the Tele-Talk unit or Radio. Group HQ would use the direction information from two or more posts to determine the exact point of detonation by using triangulation.

The end of the cold war and advances in technology eventually brought the end of the ROC and the monitoring post and group control personnel were stood down on 30 September 1991.

Amazingly hundreds and hundreds of these ROC Posts still exist (although some have been demolished) and even more amazing is that many still have the original equipment and supplies intact inside, it seems many ROC volunteers just climbed up the hatch and left everything where it was. Sadly there are also many existing ROC Posts that have been burnt out or heavily vandalised by kids.


A brighter end to this story is the emergence of ROC posts being restored for posterity, perhaps the most famous of these is 23 Post Skelmorlie in Ayrshire, Scotland. 23 Post has been totally restored and is open as a museum on certain days in the year


This is Sutton Bassett Post 11, part of the Bedford 10 Cluster.

10 Post (Cold Overton) was the Master Post with Sutton Bassett 11 and Clipston 12 making up the cluster.

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