Within WDU in 1941, assistance was given to TRE in developing a jamming system on a priority 'top-secret' basis and this is only known because of machining work done by Cyril Lingwood who remembers making gold and silver switch contacts to drawings marked up 'blanket'.
While no definite proof is available on who in WDU would have been involved, it is highly likely that Max Callender and/or Les Pugh would have been actively involved since this was their area of expertise.
Subsequent investigation has shown that the equipment was code named 'Jostle' and that a record exists in the Public Record Office (PRO) in Kew under reference AIR23/1195 with another file AIR20/1563 for a later development for 'Jostle IV'
Review of AIR23/1195 shows that it does not contain specific technical information but it does contain notes and correspondence, which while fragmented and incomplete does suggest a picture of desperate times and urgent need.
Piecing the story together it appears that sometime in the late spring of 1941, the general staff were seriously concerned about the developments in North Africa when the German Afrika Korp's under Rommel started operations and began pushing the British forces back towards the Libya Egypt border despite the Australians holding Tobruk.
It appears that TRE were asked to look for ways to hamper Rommel and they suggested 'jamming' the German radio command net (although nothing is documented in this exact manner).
This was obviously agreed and work commenced lead by a team headed by Dr. Cockburn of TRE since he reports on the 9th Oct 41 that a trial had taken place flying a Wellington bomber at 15,000 ft which was able to jam the 30M/c band from the bottom of the scale to 32.6M/cs over a 30 mile range distance.
There is then a direct reference to 'Cole' manufactured sets with a 27 to 32 M/c range and a further trial taking place between 14th November 1941 and 25th December 1941 with equipment listed as a Jammer, a power pack, a voltage control unit (from ASV MkII), a harmonic suppressor, a 80 volt 500 watt E.D.C and a 'prick' aerial.
From this it is assumed that the Jamming equipment was radiating 500 watts, which is a significant power output and to put this in perspective, is probably equivalent to the power of some smaller local radio stations.
A report of this trial in January 1942 reported that there had been complete jamming over areas within circles of 12, 25 and 50 miles with distances of 1/2, 1 and 2 miles between tank transmitter and receiver.
The next meaningful entry tells of 30 sets being fitted to 'special ops' Wellingtons being deployed to North Africa despite concerns by the RAF about loses since 3 A/C would need to fly a racetrack pattern over the battlefield at any one time and faced being shot down. There are also notes about when the A/C should be deployed due to alerting the Germans.
It appears that this 'production' equipment was designated Jostle II.
Note: it cannot be ascertained how many sets were manufactured by EKCO since no records or photos are known to exist but it is suggested that while EKCO made and supplied the component parts, assembly would have been at TRE Malvern.
A file note tells us that in Aug 42, two special ops Beaufighters were equipped with Jostle II and sent to Malta but were returned in Sept 42 as 'not suitable'.
Jostle was deployed at the start of the El Alamein battle and from PoW interrogation reports (which in the file) deemed a success since the prisoners reported just hearing 'static' in one case and another a 'wow-wowing' and it was considered that Jostle was 100% effective.
Notwithstanding this the file contains comments from 8th Army who seemed less than impressed and expressed reluctance to proceed and the RAF who expressed concern about aircraft loses to both ground fire and aerial attack, which were as predicted.
Despite this lack of enthusiasm, it is assumed that Jostle did continue to be used although the file does not contain any further entries.
The second file (AIR20/1563) is slightly more informative since it has a structure and starts as meeting minutes of a committee set up to consider airborne jamming of German fighter command nets in Europe.
The attendance list shows TRE, RAF, Air Ministry, USAAF and Metro Vickers as attendee's. It discusses the need for both Lancaster's and Fortresses to be equipped with an updated Jostle to be designated Jostle IV.
Dr. Cockburn states that the aim is to have a 'barrage Jammer' of 500 watts which might also be used as a driving stage for an additional 2kw output and must be capable of operating over a 20 to 80M/c range but preferably over a 10 to 160M/c range and offer an improvement of 10-20Db over Jostle II.
Reading through the subsequent minutes it is apparent that Metro Vickers was the designer and manufacturer, however it is known that WDU acted as the sub contractor to TRE for the prototype unit and its known that Jimmy Smith in the WDU model shop made the pressurised canister since this equipment needed to be pressurised for safe operations at the high altitudes flown by the Flying Fortresses and even some Lancaster operations.
