Knickebein, Mow Cop and Aspirin

Author: Geoff Wright

During the war the Mow Cop hilltop saw service, when the RAF used it for some revolutionary secret work, that helped save countless lives.

The German air force used a system of two intersecting radio beams (“Knickebein”) to guide aircraft to their targets. At the point of intersection of these two beams the bomb cargo was unloaded. The RAF unit was a small installation on the hill top that disrupted these beams, causing the Germans to drop their deadly cargo off target. There were 35 similar installations scattered across the country in 1941. In the early days it was discovered that radio diathermy units used in hospitals could be modified to Knickebein frequency and they were placed in police stations and other sites until better equipment was available.

The Knickebein system was code named “Headache” by the RAF and the countermeasures logically  “Aspirin”.

Another codeword used by the RAF was “Starfish” which stood for decoy sites near major targets such as RAF airfields or cities. One of these was located near Cranage.

The first decoys were airfields – “K” Sites – for day use, set out on large fields, heath or warren land, and sometimes on disused WWI aerodromes.  Props would include dummy aircraft of similar type to those used by the stations they were protecting.  There would be mock bomb dumps and fuel stores, and the surface would be levelled to look like a landing ground.  Impressed civilian aircraft, such as D H Moths, were employed on some sites to resemble Tiger Moth military training aircraft.   Large sheets of canvas were painted and laid on the ground to represent hangars while, in some cases, old and disused vehicles were set around the site along with gun pits and camouflage nets.  These dummy airfields looked very realistic from the air.  The crews had their own buildings and trucks.   Most “K” Sites were closed down in 1942/43 although a few were still in use in 1944.

In total, there were approximately 630 Decoy Sites in the United Kingdom, of which 230 were decoy airfields and 400 were decoy towns, marshalling yards steelworks, foundries and factory complexes.