The Belvedere guys always started up unstrapped and side windows wide open ready to evacuate if needed, as Avpin was used.
I was fire officer at Seletar in 1967 and the resident squadron of Belvederes (no 66) were a constant worry. The year before one had burned out on the pan after a start up fire on the occasion of the annual AOCs inspection. I also remember reading an accident report on another one where the fire had been successfully put out by the groundcrew. The section on casualties read "Fatalities - nil, Injuries - one - pilot broke his ankle jumping out of aircraft!"