Hailed by the contemporary motoring press as “the fastest full four-seater in the world” upon its July 1972 launch, the original XJ12 evolved through three series.

The last of these arrived in April 1979 and saw the sleek silhouette that marque founder Sir William Lyons had penned revised by Pininfarina.

As well as an airier glasshouse, the newcomer featured flush-fitting door handles, re-profiled tail lights (with integral reversing lights) and surprisingly elegant impact bumpers.

Often compared to the Mercedes-Benz S-Class and Rolls-Royce Silver Shadow, the Series III XJ12 was among the most accomplished luxury saloons of its generation.

Noted for the refinement of its fabulously smooth 5343cc SOHC V12 and slick three-speed automatic gearbox, criticisms as to fuel economy were alleviated to some degree by the introduction of a new H.E.

engine in 1981.

Despite developing more power and torque (some 299bhp and 318lbft respectively) courtesy of its redesigned Michael May cylinder ...