There was also a well-known instruction NOT to 'dip' the tanks during refuel as that would cause the refuelling system to think that a tank had been refilled when it was only partially full........IIRC!
Sit, watch, don't touch!
Sadly it still happens today. Recently, we spent ages sorting out a new tanker aircraft's Mission Computer system after 'hangar pilots' had given themselves some 'training' on the system overnight.............
