You had nothing to fear as you would never walk alone...
Indeed. There had to be a minimum of two of you, each of whom was "capable of detecting an unauthorised act or incorrect procedure on the part of the other".
RAFASUPU at Collyweston ran the 'hydrogen bomb courses', although there was a fluffier title. There was nothing like a Stamford-induced vindaloo and Ruddles hangover at 08:00 the following day when being taught the Pauli exclusion principle and other elements of nuclear physics theory by some long-suffering chap in a white dustcoat...
SPDF means....??