text: The Lancasters of 617 Squadron flew around Bremen then found that there was cloud on the north side of Bielefeld forcing PD112 S with the Grand Slam to attack from the south after resetting the SABS, followed by the photographic Mosquito. One of the 105 Squadron Oboe Mosquitoes dropped four  Target Indicator bombs which landed about  to the south-south-west of the target. At  and from , a far from ideal height, the Grand Slam fell from PD112 S, which jumped  higher at the loss of weight. After 35 seconds, the bomb hit the ground about  short and exploded the site erupting as the Tallboys came down. The pilot of the photographic aircraft, which recorded the attack from  shouted "You've done it!". The effect of the Grand Slam could not be distinguished from that of the eleven Tallboys but photographic reconnaissance by a Spitfire from 542 Squadron, following the bombers, then a Mosquito from 540 squadron later on, showed that  of the north viaduct and  of the south viaduct had been demolished, depositing about  of rubble into the valley.
  Arnsberg, 15 March
  On 15 March, in a haze with some cloud over the target, two aircraft of 617 Squadron with Grand Slams fuzed for 11 seconds' delay and 14 Lancasters of 9 Squadron, carrying Tallboys, attacked the railway viaduct at Arnsberg again. A close fighter escort of 34 Mustang Mk IIIs was provided by 11 Group. A photographic Mosquito, KB433, was laid on by 627 Squadron and another 141 fighters were in the vicinity covering raids by 4, 6 and 8 Groups. The  long viaduct, built from brick and stone faced with concrete, crossed the Ruhr in five spans. In poor visibility the crew of the photographic Mosquito saw that "the whole force made one run into sun and one bomb seen to drop". This was the first Grand Slam, dropped from  at