Roland Beamont had the 20 mm cannon on his Tempest adjusted to converge at ahead. This was so successful that all other aircraft in 150 Wing were thus modified. The anti-V-1 sorties by fighters were known as "Diver patrols" (after "Diver", the codename used by the Royal Observer Corps for V-1 sightings). Attacking a V-1 was dangerous: machine guns had little effect on the V-1's sheet steel structure, and if a cannon shell detonated the warhead, the explosion could destroy the attacker. In daylight, V-1 chases were chaotic and often unsuccessful until a special defence zone was declared between London and the coast, in which only the fastest fighters were permitted. The first interception of a V-1 was by F/L J. G. Musgrave with a No. 605 Squadron RAF Mosquito night fighter on the night of 14/15 June 1944. As daylight grew stronger after the night attack, a Spitfire was seen to follow closely behind a V-1 over Chislehurst and Lewisham. Between June and 5 September 1944, a handful of 150 Wing Tempests shot down 638 flying bombs, with No. 3 Squadron RAF alone claiming 305. One Tempest pilot, Squadron Leader Joseph Berry (501 Squadron), shot down 59 V-1s, the Belgian ace Squadron Leader Remy Van Lierde (164 Squadron) destroyed 44 (with a further nine shared), W/C Roland Beamont destroyed 31, and F/Lt Arthur Umbers (No. 3 squadron) destroyed 28. A Dutch pilot in 322 Squadron, Jan Leendert Plesman, son of KLM president Albert Plesman, managed to destroy 12 in 1944, flying a Spitfire. The next most successful interceptors were the Mosquito (623 victories), Spitfire XIV (303), and Mustang (232). All other types combined added 158. Even though it was not fully operational, the jet-powered Gloster Meteor was rushed into service with No. 616 Squadron RAF to fight the V-1s. It had ample speed but its cannons were prone to jamming, and it shot down only 13 V-1s. In late 1944 a radar-equipped Vickers Wellington bomber was modified for use by the RAF's Fighter Interception Unit as an airborne early warning and control aircraft. Flying at an altitude of over the North Sea at night, it directed Mosquito and Beaufighters charged with intercepting He 111s from Dutch airbases that sought to launch V-1s from the air. Disposal The first bomb disposal officer to defuse an unexploded V-1 was John Pilkington Hudson in 1944. Deception To adjust and correct settings in