I can't back this up with evidence, but I believe the beginnings of Perf "A" stem from work done by a "Hazel" Hazelden, who was on No 2 ETPS course back in the forties. He introduced the idea of V1, figuring that there was no need to die if an engine failed. He was a test pilot with Handley Page, and finished his flying career with Air Anglia on the F27, where I was fortunate enough to have him teach me a few things about flying.