After a massive domination in the 1950s with 5 victories, Jaguar decided to return to Le Mans and compete against Ferrari and the rising Fords with a new car called XJ13. Once again body exterior was designed by Malcolm Sayer, the aerodynamicist responsible for aerodynamic air flow work on the successful racing cars C-type, D-type and road E-Type. Sayer used his Bristol Aeroplane Company background to build it using techniques borrowed from the aircraft industry. Construction began in 1965 with first (and only prototype) running by March 1966.
The development of the V12 XJ13, although treated seriously by the designers, was never a priority for company management and became less so following the 1966 merger with British Motor Corporation. By that time Ford also developed the 7 liter GT40, and so the XJ13 was already considered obsolete when prototype was completed. Suspicious was confirmed when it was tested at MIRA (Motor Industry Research Association) track and at Silverstone circuit. Additionally, up and coming regulations would soon restrict engine size to 3-liters. To run cars with larger engines, manufacturers had to build fifty examples as production cars (later reduced to twenty-five). The conclusion was that the project would have required considerable development and resources to make it competitive. The prototype was put into storage and no further examples were made.