The 1966 Jaguar XJ13 is a one-off prototype and one of the most beautiful ‘what-ifs’ of the sixties. Once thought of as a potential Le Mans entrant, it was surpassed by the all-conquering Ford GT40 and never raced, despite its immense 502 bhp. It was however a prototype for Jaguar’s V12 engine which stayed in production for 25 years. The fantastic sixties body was the work of Malcolm Sayer who in the C, D and E Types created some of…