text: A post-war report recorded six hits by Tallboys, the two Grand Slams and the other Tallboys landing in the water. The six Tallboys had penetrated the roof part way, hit girders and exploded, blowing holes through the ceiling and depositing hundreds of tons of concrete into the pens. There had been 3,000 people inside the pens, fewer than usual, because it was Poets Day, when German workers left at ; 27 people were killed, about sixty were seriously injured and a panic ensued; U-906 and U-1192 were damaged. About thirty Me 262s appeared and 467 Squadron RAAF, on the oil tanks raid, accelerated and turned, ending up bumping along behind the 617 Squadron slipstream. The Mustangs jettisoned their drop tanks and 122 Squadron bounced the German jets which raced away. The Polish 306, 309 and 315 squadrons attacked the jets and claimed three Me 262s shot down and three damaged; two Lancasters were shot down.
  Heligoland, 19 April
  The coastal gun batteries on the islands of Heligoland and Düne in the Heligoland Bight, the south-eastern extremity of the North Sea, were attacked on 19 April. The military installations on the main island comprised a radar installation covering the Elbe and Weser rivers, an airfield and a coastal battery each with  and  guns. To ensure that Allied ships could enter the Elbe and Weser estuaries, Bomber Command intended to attack the island with  bombs but at least forty heavy anti-aircraft guns on the islands had to be silenced. The gun positions had a diameter of about  and only hits or near misses would be effective. On 18 April, 969 bombers had attacked the anti-aircraft guns but some remained operational. On 19 April, 20 Lancasters of 617 Squadron attacked with six Grand Slams and fourteen Tallboys; 16 Lancasters from 9 Squadron carried Tallboys fuzed for 25 seconds' delay.