The contact to begin development of AI Mark 20 was awarded in late 1953 and was for a limited number of sets (probably no more than 5) and was almost certainly given to the company because of the existing work going on with the 'Blue Sky' (Fireflash) radar system where to a certain extent the performance parameter were similar although AI 20 was to be physically larger.
The granting of the development contract by TRE was as a result of problems Ferranti were having getting the Ai Mark 23 (Air pass radar) configured and working, which to be fair the them was as much due to changing operating requirements by the RAF, one of which was the decision to adopt the 'Firestreak' infrared homing missile and not helped by the fact that the whole fighter contact was running late (almost a British tradition??).
The design was to be unique since the radar had to sit in an enclosed housing, which formed the 'shock-cone' inside the nose of the aircraft used to slow the air entering the engines down.
The AI-20 team was headed up by Cyril Drew supported by Bill Graville, Ron Beaven (CRT unit), Henry Cox, Mike Skinner, John Radlett, Ted Smith and Ian Walker (the personnel involved changing periodically).
The strobe unit subsystem was done by John Yarrow (assisted by Henry Cox) and his team from 'top lab' where they were working on project 'Blue Sky'.
Most power supplies, certainly the Transformers and wound products were designed by Ian Walker and John Clark and some additional re-design work was possibly done by Norman Jerrum (ex TV and Radio designer) at Southend.
Gibby and his team including Eric Alden were responsible for the mechanical design.
Norman Wall and his team were responsible for The 'IF' unit.
Hugh Green and his team, which included Harry Robinson and Tommy Morgan (although there was at least one other), headed the waveguide design team.
Ray Reeves designed the Klystron control unit.
The Radar Labs draughtsmen were under the leadership of section leader Jack Timms, together with Horace Fowler, Jim Bye and a couple of others. For secrecy, this D.O. section was in a separate partitioned off part of the main D.O. and due to the secrecy, non-participating Radar folks were not welcomed! Note Gibby had his own draftsmen assigned to him, one of which was Stan Seager, later joined by Len Newborough.
Cyril and his team were in ensconced in 'her ladyships bedroom' since this room had the space to house the chassis of the equipment, which was mounted on a special rotatable jig, which in turn was on casters since this equipments was physically larger than any unit made before and was technically challenging to say the least. This laboratory also had an advantage of having large 'French style window doors, which opened up a large area such that the transmitter could be powered up pointing outside over the top of the canteen into free space although usually this power was put into a dummy load.
AI-20 was to be a high-powered 'X' band system of about 100Kw output using a using a 5C22 hydrogen thyratron modulator. Interestingly the operating frequency and the Pulse Repetition rate remain secret to this day (2007) due to its later incarnation as 'Red Steer'.
Much new ground was broken in the design and development of AI-20 not least of which was the use of honeycomb structure in the main chassis (to save weight) but also in the waveguide run where part of the waveguide run was machined as two halves out of solid aluminium and then mated together. This entailed a very high degree of workmanship due to the very tight tolerances.
