The aircraft borrowed design elements from several predecessors, including an enlarged wing from the T.8 Kirby Tutor, and a fuselage, reminiscent of the early Falcons, with cabane struts in front of the rear cockpit, which sat in front of the narrow cabane structure under the centre-section, as well as an additional cockpit in the nose.
[1] During the intensive carrier operations of the war it had been noticed that there were many accidents as aircraft neared the 'Round-down' (the aft edge of the flight deck) on their approach to 'Land-on'.
John Sproule, former designer at Slingsby, was ordered to find a suitable aircraft and carry out the test flying.
[1] The T.20 was fitted with special instrumentation and large Zap flaps, fixed at 30°, at Wombleton aerodrome where initial trials were carried out at low altitude towed behind a car.
Initial flights with Sproule at the controls went well, but his deputy's first outing ended in disaster as the pilot failed to pull back on the stick to climb away, staying close to the deck weaving from side to side till eventually the tow cable snagged a telecoms antenna and unceremoniously dumped the T.20 into the sea alongside the carrier.