In mid-1944 the British had to realize that with traditional weapons (torpedoes, mines and bombs) there was no way to put the Tirpitz out of commission permanently. At this time a new bomb was put into service, the "Tall Boy", a weapon developed under the direction of Professor Dr. Barnes Wallis, under whose leadership the 3.900 kg (8.600 lb) rotary water bombs, used with great success in the spring of 1943 on reservoir dams in Germany, also originated. The RAF Bomb Command thus received orders to attack the Tirpitz with the new "Tall Boy" bombs. With their weight of 5.443 kg (12.000 lb) they were the heaviest bombs ever built up to that time. In fact, the "Tall Boy" was a "Superbomb". It belonged to the category of thick-walled, teardrop-shaped GP bombs (GP "General Purpose", thus a multipleuse bomb) and were 6,35 meters (21 feet) long with a diameter of 0,95 meter (38 inches). Their warhead consisted of 2.358 kg (5.200 lb) of "Torpex", a highly explosive substance with a detonation speed of 7.600 meters (8.350 yards) per second (in comparison: the detonation speed of traditional TNT is "only" 6.900 meters (7.580 yards) per second). The ignition delay could be set to a maximum of eleven seconds. Such bombs could be carried only by the four engined bombers of the "Lancaster Mark I S" type, and then only one per plane, which also had to be rebuilt for this purpose. At the end of the war a total of 854 "Tall Boy" bombs had been dropped, of which 77 were dropped in the three attacks on the Tirpitz in September, October and November of 1944 alone. In the first attack, two direct hits on the bow was achieved, in the second only a near miss. In the decisive third attack there were three direct hits and one near miss. At the third attack, 12. November 1944, Tirpitz capsized and had to be written off as a total loss.