Looking down the entrance shaft of the Royal Observer Core bunker at Inverharroch.

And another fascinating glimpse into Cabrach history with a look at the role that Inverharroch and the Cabrach played in protecting Great Britain during the Cold War years.

Some may have noticed a strange bit of pipework poking out of the ground on the grassy mound next to Inverharroch and this is the only sign of the  Royal Observer Core monitoring post hiding beneath the surface.

Royal Observer Corps monitoring posts are underground structures all over the UK, constructed as a result of the Corps’ nuclear reporting role and operated by volunteers during the Cold War between 1955 and 1991. Over 1500 of these were constructed across the UK.

The posts were part of the British government’s ‘four-minute warning’ system, reputedly enough time for the public to be warned of an imminent nuclear strike and get to safety! The Royal Observer Corps 29 Group HQ in Aberdeen would have used information from this post (Post 32) and others to report the locations of likely nuclear bomb drops, measuring the power and pressure of the detonation.

The Cabrach Post, opened in June 1960 and closed September 1991 and is designated a regionally significant site. The note in sites and monuments listing states that ‘The surface features remain, within a small rectangular compound, but internally the post has been stripped’.

Inside the ROC monitoring post

Inside the ROC monitoring post

In all but a very few instances the posts were built to a standard design consisting of a 14-foot-deep access shaft, a toilet/store and a monitoring room, with 12 inch thick reinforced walls and roof, access hatch and metal ventilation louvers which could be closed to avoid contamination by radioactive fallout. The whole structure was then bitumen tanked to waterproof it and covered over with earth to form a grassy mound. The protection provided by the concrete roof and compacted earth mounded above the post was estimated to reduce any external nuclear radiation by a factor of 1,500:1.

The observers, most of whom were volunteers, were sealed inside the bunker with bedding and rations and monitoring was carried out with monitoring instruments protruding through two metal pipes in the roof of the bunker.

A small number of these posts have been restored and are open to the public including the ROC Post Museum at Arbroath and Skelmorlie and the Secret Bunker at St. Andrews in Fife.

Thank you to Ronnie Sheed for the following update on the ROC Post

The ROC posts were arranged in groups of three with the master post having the capability to contact HQ by radio in the event of the landlines failing.

Cabrach was grouped with Drummuir and Grange with the latter being the master.

I was an ROC volunteer with both Drummuir and The Cabrach in the 70’s and early 80’s and have spent many a cold night in the post during 24 and 36 hour exercises.


ROC monitoring posts

The Four-minute warning

The Cabrach ROC Post

The Cabrach ROC Post

York Cold War Bunker

Royal Observer Corps Heritage (ROCA)

ROC Post Museum, Arbroath & Skelmorlie.

Scotland’s Secret Bunker, St Andrews, Fife

Thank you to Marina Alexander (doricma) who once again pointed me in the right direction for this little piece of research