This particular car, a 1973 long wheelbase model, was supplied to Her Majesty Queen Elizabeth the Queen Mother, replacing Her Majesty’s previous Jaguar, a 1955 Mark VIIM which was then returned to the Jaguar company. Her Majesty’s new car was specially finished in the Royal colour of Claret, and uniquely among Jaguars, was fitted with the special Vanden Plas interior as found on the equivalent Daimler. Many years later, Her Majesty expressed the wish that on her death, this Jaguar should also return to the company, which duly happened on Her Majesty’s passing in 2002.

The original XJ6 launched in 1968 was a tremendous success for Jaguar, but behind the scenes another new even more remarkable model was being prepared. Since the mid-1960s, Jaguar’s engineers had been at work on the design of a V12 engine, which was launched in the E-type Series 3 in early 1971. However, this engine was always intended for the new saloon car, and in 1972 the XJ12 finally appeared: the world’s only V12-engined saloon.

This car had an enormous impact. Coupled with the high standards of refinement and comfort of the XJ6, the new 5.3 litre engine gave the XJ12 a top speed of 146 mph (235 km/h), and the list price at launch was only £3,725. Externally, the main difference from the XJ6 was a new radiator grille with simple vertical bars. For the first time, serious comparisons began to be drawn between Jaguar and Rolls-Royce, and it seemed that the XJ12 was a worthy contender for the title of “Best Car in the World”.

If there was any criticism of the new model, it was that it was short on passenger space, particularly in the rear seat, but this was soon rectified by the introduction of a long wheelbase model at £4,052.

A Daimler version revived the old name Double Six. Long wheelbase Daimlers were given a special interior by the old coachbuilding firm of Vanden Plas in London.