 In 1955, the "Two-point-four" or 2.4-litre saloon (named by enthusiasts 2.4 Mark 1) was the first monocoque (unitary) car from Jaguar.Its 2.4-litre short-stroke version of the XK engine provided performance.In 1957, the 3.4-litre version with disk brakes, wire wheels and other options was introduced, with a top speed of .