The 4000 lb bomb was also referred to as the 'Blockbuster'. The only aircraft capable of delivering it at the time stationed on Malta was the Wellington bomber. First used on the night of 16 - 17th October 1941 where a heavy raid was carried out on Naples. Targetted areas included docks, factory buildings, the Arsenal & a torpedo factory. Also loaded were the usual 1000 pounders. This was the first use of the Blockbuster anywhere in the Middle Eastern theatre. Specially adapted aircraft were used to fit these bombs into the bomb bay. My father worked on the first of these aircraft.
Pilots were instructed not to bring the bomb back as the undercarriage could not support the weight.

4000 lb Block Buster