ROC Post Threlkeld must be in one of the most scenic locations of all the 1563 Observer Corps observation posts all over the UK which were established or repurposed from wartime use in 1956.
It’s an underground concrete bunker designed to resist nuclear attack, a “Protected Post”. The floor is about 5 m. below the access hatch and is reached by a vertical ladder. There’s a ventilator at the other end of the underground chamber, the dimensions are about 5 m. x 2 m. x 2 m. There’s a telephone line but no mains electricity or water. An observation platform was also required, ROC Keswick/Threlkeld has a small tower built of local stone for this purpose.
ROC Post Threlkeld site is adjacent to the old main road between Keswick and Threlkeld and within sight of a number of Cumberland fells. Its function in the Cold War was to observe and report the spread of radioactive fallout from a nuclear attack. ROC Threlkeld would have been manned by volunteers. The methods of detection were primitive and imprecise and had to be reported on the telephone in to a structured reporting organisation, also built on wartime methods. Those transparent maps with aircraft symbols being moved by Wrens that are iconic of WW2 movies are the top level of the Observer Corps reporting network.
The resilience of the ROC telephone network was based on principles first established in the Battle of Britain: posts were organised in triangles so that each post always had at least two routes for reporting. There were many reorganisations but at the end of active service, ROC Keswick/Threlkeld (J3) worked with ROC Penrith (J2) and ROC Bassenthwaite (J1), all reporting to No. 22 Group headquarters in Carlisle.
The survival of the Observers, who were exposed to the radiation they were reporting, was not expected to be more than a few days following a nuclear attack, but the reports they would have contributed were considered critical to plot the spread of fallout and to plan the management of its deadly effects.
Non-lens photography was the main method of detection of radiation. 10x8 sheets of Bromide paper were stored in radiation-resistant containers, eg a lead wallet. Then two sheets were exposed orthogonally but still protected from light. After a standardised development it was possible to estimate the amount and direction of the radioactive fallout. This was then compared between posts to give an estimation of the drift of the cloud of radioactivity.
The Observers did what they could to be comfortable but the bottom line is that although their post looks picturesque on a fine April afternoon, less so when confined 5 m. underground during an alert, on exercise or for real. In the overnight frost, fighting condensation on the walls and damp in your kit. Primitive sanitation and no mains electricity...
The Royal Observer Corps was stood down in 1995 and the Posts returned to farmland or sold at auction. ROC Post Threlkeld now appears to be in the care of “Carlisle Group ROC Post Heritage”.
I had the opportunity to buy a similar Post which had been reporting to No. 6 Group, Norwich. We used it for a few years for re-enactment activities but I needed to sell it in 1999; sadly, it is now derelict. Hiking past the Threlkeld post was nostalgic but also heartening to see that at least a few of these historic places are still being looked after.
My hike to Threlkeld was through the gorge of the River Greta, the river now looking serene after last month’s heavy rains have dispersed. Back via Keswick Climbing Wall café and Castlerigg sone circle.