This 420G was built in May 1969 and was originally sold to a firm of paper makers in Manchester. They still owned the car in 1985, when they generously donated it to the Jaguar Daimler Heritage Trust.

In 1961, the big Jaguar Mark IX saloon was eleven years old and rather out of date. A much-needed replacement was introduced at the London Motor Show that autumn. The new car, naturally called the Mark X, was a bold step forward for Jaguar. While the previous model had a separate chassis, the new car featured unitary body construction and was at that time the largest car in Britain to use such a body. It also had independent rear suspension, similar to the E-type which had been launched in March 1961.

Fitted with the 3.8 litre XK engine in three-carburettor form, despite its size and weight – this was the largest Jaguar ever made, weighing close to 2 tons – the Mark X was no sluggard and offered a top speed of 120 mph (193 km/h). Five passengers and quantities of luggage could travel in supreme comfort. In typical Jaguar fashion the price was unbelievably low, at only £1,640 basic at launch or just under £2,400 including Purchase Tax. The real price to be paid was fuel consumption of around 15 mpg (19 litres/100 km).

Although warmly welcomed at the time, the Mark X did not sell as well as expected. Early cars had different teething troubles. Matters were improved with the 4.2 litre version introduced in 1964, with improvements to the power steering, brakes and transmission. Air conditioning and electric windows were now available as options.

The final version was the 420G of 1966, which had a side chrome trim strip, new radiator grille and wheel trims, and was often seen in two-tone colour schemes.

After the launch of the new XJ6 in 1968, production of the 420G ran down in 1970, with a total of just over 24,000 of the Mark X/420G family having been made.