Another high altitude fighter version. It was thought that the Germans would use high altitude bombers to strike at Britain, unhindered by Fighter Command’s current equipment. The development of the Mk VI and then the VII was very much an insurance policy against such a development. The VII had the Merlin 61, 64 or 71 engine, with two stage supercharger giving 1,660 hp (Merlin 61). The two stage supercharger revolutionised the performance of the Spitfire at altitude. Previous Merlin’s performance had died away above 20,000 feet. The new Merlins astounded pilots by their ability to keep on going up and up! The VII kept the extended wing-tips and pressurized cabin of the VI but added a retractable tail-wheel. Many had a pointed tail-fin. Small leading-edge fuel tanks increased range. Armament was of the “B” type; two cannons and four machine guns. The new Merlin introduced two equal sized radiators, one under each wing. Previous Spitfires had an asymmetrical arrangement with radiators of unequal size. The VII could reach 44,000 feet. 140 MK VII Spitfires were produced.