text: The bomb was not to be dropped from under  but Martin, the pilot, could not coax the bomber above . On its five-minute bombing run, Martin had to fly within the tolerances of its SABS bombsight, within  of airspeed and +/-  of altitude. The cameramen started filming and when the bomb dropped, PB966 C jumped  higher. The bomb began its spin and came down on the western span, which disintegrated, along with the roofs of buildings nearby. All but one Lancaster of the first wave, whose Tallboy hung up, bombed. A second wave bombed fairly accurately but one Grand Slam fell  off line due to a SABS fault. Two spans of the bridge, about  long and one pier had been destroyed, the track on the west bank had been cut,  of one of the embankments had been shoved out of line and the entrance to a tunnel on the east bank had been blocked; no damage had been caused to a Red Cross camp nearby. After the war the casings of a Grand Slam and a Tallboy were found at the site; the Grand Slam was thought to have landed flat on a road and only the explosive at the rear of the casing detonated; the Tallboy hit a wall, broke up and buried itself in the ground without going off.
  Arbergen, 21 March
  Twenty Lancasters of 617 Squadron, two carrying Grand Slams and the rest Tallboys, flew in good weather with little cloud to Bremen to attack the double-tracked railway bridge at Arbergen which crossed the Weser near Nienburg. The bridge was  long with three steel girder spans. The railway approached the river from the south-west along an embankment until  from the river where it crossed a meadow on a low-lying steel viaduct resting on piers. The bombers were escorted by twenty Mustang Mk IIIs of 306 (Polish) Squadron and 309 (Polish) Squadron. Another five fighter squadrons were provided to escort a day raid by 1 and 8 Groups on an oil refinery at Bremen; other Main Force aircraft attacked targets in Münster and Rheine.