The Jaguar Mark X was a large beautiful saloon made by Jaguar Cars and was the largest Jaguar ever produced. It was announced at the London Motor Show in the same year as the Jaguar E-Type, though seven months later, in October 1961. The Mark X featured a 265 HP 3.8 litre six-cylinder engine with twin overhead camshafts and triple SU carburettors. The engine was quite similar to the one used on the E-Type. The transmission featured a four-speed manual gearbox or an automatic with optional overdrive. Power-assisted steering, independent rear suspension and four disc brakes were standard features.
The Mark X acquired a 4.2 litre straight-six engine in 1964 and a newly developed all-synchromesh four-speed gearbox. In October 1966 the Mark X was renamed the Jaguar 420G with changes in styling and interior design. There were, however, no mechanical changes. Changes to the interior included perforations in the central sections of the leather seats, padded dashboard sections and optional air conditioning.
The 420G could be differentiated from the Mark X with a vertical central bar splitting the grille in two and side indicator repeaters on both front wings. The hub caps too were changed and a chrome strip ran down both sides of the car. It was also available without the chrome strip in a two-tone paint scheme. The 420G was also offered in limousine version with a dividing glass screen partition on the standard wheelbase which was later extended by 21 inches. The last Mark X was produced in 1970 to be replaced by the Jaguar XJ6.