Series 1 (1968–1973)
The XJ6, using 2.8L (2790cc/ 170in³) and 4.2L (4235cc/ 258in³) straight-six cylinder versions of Jaguar's renowned XK engine, replaced most of Jaguar's saloons – which, in the 1960s, had expanded to four separate ranges. An upmarket version was marketed under the Daimler brand and called the Daimler Sovereign, continuing the name from the Daimler version of the Jaguar 420. The "XJ" designation was from the car's code name during development, standing for Experimental Jaguar.
The car was introduced in September 1968. Power assisted steering and leather upholstery were standard on the 2.8 L 'De Luxe' and 4.2 L models and air conditioning was offered as an optional extra on the 4.2 L. Daimler versions were launched in October 1969, in a series of television advertisements featuring Sir William. In these spots, he referred to the car as "the finest Jaguar ever". In 1972 the option of a long wheel base version, providing a modest increase in leg room for passengers in the back, became available.