The Rover P5 is a series of large saloon and coupé automobiles that were produced by Rover from 1958 until 1973. The models were marketed under the names Rover 3 Litre, Rover 3.5 Litre and Rover 3½ Litre. The P5 was a larger car than the P4 which in some respects it replaced. 69,141 units were built. A major step ahead for Rover came with the P5 model of 1958, a large luxury saloon with a 3-litre version of Rover's six-cylinder Inlet Over Exhaust (IOE) engine carried forward from the Rover P4 series. It was the first Rover car with unitary bodywork, styled by David Bache. This model combined elegance with dignity, and had a traditionally well-appointed interior. Later developments of the P5 included the more rakish coupe with a lowered roof line, and the 3.5 litre V8 model of 1967 which for the first time used an all-aluminium V8 engine design purchased from the Buick Motor Division of General Motors Corporation in the United States. The 3- and 3.5-litre models became favourites for transport of dignitaries, including British Prime Ministers from Harold Wilson to Margaret Thatcher. HM The Queen also used several Rover P5 cars for her private motoring. Mark I The P5 appeared in September 1958, badged as the "3-litre". It was powered by a engine. This straight-6 IOE engine used an overhead intake valve and side exhaust valve, an unusual arrangement inherited from the Rover P4. In this form, output of was claimed. An automatic transmission, overdrive on the manual, and Burman power steering were optional, with overdrive becoming standard from May 1960. Stopping power came originally from a Girling brake system that employed drums all round, but this was a heavy car and by the time of the London Motor Show in October 1959 Girling front power disc brakes were fitted. The suspension was independent at the front using wishbones and torsion bars and at the rear had a live axle with semi-elliptic leaf springs. A Mark I-A line, introduced in September 1961, featured a minor restyle with added front quarter windows, intended to "assist the dashboard ventilation". Under the metal, the 1A featured modifications to the engine mountings and the automatic transmission and hydrosteer variable ratio power steering as an option. By 1962, when production of the original Mark I series ended, 20,963 had been produced. An automatic version tested by The Motor magazine in