After several fatal crashes in 1957 all the Swinderby Vampire FB5 & 9's were grounded for a month after they were found to be twisted beyond safe limits. Badly dented bullet fairings around the tailplanes/fins were also blamed for the loss of control during high speed/mach dives. When our then senior course was extended by two weeks they made us fill the time in cleaning and polishing all the Vampires chosen to be re-rigged and de-dented.