"In the last war, a twenty pound bomb was considered pretty grim..."
As the video points out among the excellent footage, the aircraft were the limiting factor. In this photo the first of the "Blockbuster" 4000 pounders to arrive in Malta in 1941 is loaded onto a Wellington bomber. At the time this was the only aircraft in Malta that was capable of picking the bomb up.
First used on the night of 16 - 17th October 1941 where a heavy raid was carried out on Naples. Pilots were instructed not to bring the bomb back as the undercarriage could not support the weight.