Sycamore - Westlands ISTR. The aircraft went through substantial testing with various accelerometers fitted to assess the engineering penalties for each manoeuvre and a couple of aircraft at Wallop were allowed to be used (they had G meters fitted).
The purpose was to allow the Blue Eagles display team to fly 1 Lynx and 4 Gazelles during the display season each year. It wasn't just cuffed on the back of a fag packet.