text: The bomb dump at Woodhall Spa had been limited to forty Tallboys but room was made to accommodate ten Grand Slams by removing ordnance not in use. In February the A&AEE used PB592/G, a Lancaster B.Mk1, to test loading the Grand Slam using the Type H bomb trolley, which had been designed for the Tallboy and Grand Slam. When the first bomb was moved with an Allen crane, its front wheels rose from the ground as the bomb was lifted and the bomb could not be lowered smoothly, only by unlocking and locking the brake, which dropped the bomb  each time. The armourers used a US Bay City crane afterwards with a power-lowering unit added early in 1945.
  Grand Slam test
  The A&AEE at RAF Boscombe Down had only one bomb to test, with 617 Squadron standing by with the rest, ready to commence operations. The bombing range at the Ashley Range in the New Forest had a concrete target about , to be bombed preferably from the optimum height of . PB955 was loaded with the Grand Slam to be flown by Group Captain H. A. (Bruin) Purvis; bad weather led to two failed attempts to bomb due to mist obscuring the target. On the third attempt, PB592/G, flown by Squadron Leader Headley (Hazel) Hazelden, managed to drop the bomb on 13 March. The aim of the crew was accurate for distance and observers saw the black and white painted bomb rotate as it fell, about  off line to starboard. After release, the Grand Slam accelerated to , near supersonic, penetrating deep underground before detonating. The bomb exploded and left a crater  in diameter and  deep; 617 Squadron was phoned from a nearby pub and told of the success; formal permission to use the bomb was given on 22 March and operations began the same day.
  Grand Slam operations, 1945