The front-end styling of the Daimler DS420 limousine introduced in 1968 shared a family resemblance with a Daimler grille mated to a four headlight nose.
The 420/Sovereign range began to be replaced by the Jaguar XJ6 in September 1968. The Jaguar ceased production in December 1968, the Daimler remaining in production until July 1969.
A new XJ6-based Sovereign was introduced in October 1969. Once again, it was externally virtually identical to its Jaguar source car with the exception of its fluted grille and Daimler badging. This Sovereign was offered with either the 2.8 litre or the 4.2 litre version of the XK engine.
The Daimler Sovereign name remained in use for the Series II version of the XJ6, with a raised front bumper and shallower grille; an extended wheelbase version was introduced, which eventually became the standard model. From 1975 the 2.8 litre was replaced by a 3.4 litre version of the XK engine.
The Series III XJ6 range, with new bumpers and revised roofline, initially continued to include a Daimler Sovereign, but in 1983, during the run of the Series III, the range was re-named with the base model named the Jaguar XJ6, the more luxurious version named the Jaguar Sovereign, and the top-of-the-range simply known as the Daimler, without a model name.
Jaguar introduced a short-lived two-door pillarless coupé version of the Series II using the short wheelbase floorpan and Daimler versions using both six and twelve cylinder engines were also available.
From 1972 Jaguar's 5.3 litre V12 engine was available in the XJ range, and for the Daimler version a name used by the company from 1926 to 1938 was revived. Unlike the Jaguar, the twelve-cylinder Daimler had the same radiator grill as its six-cylinder sibling, and externally only the badges distinguished them.
Although the Sovereign name was transferred to Jaguar, the Double Six name remained with Daimler throughout Series III production, which continued until 1992.