The Daimler DS420 limousine was introduced in June 1968 to replace the elderly Vanden Plas Princess 4 Litre DM4 and Daimler DR450 limousines. Based upon the Jaguar Mark 10/420G platform, the new Daimler was powered by Jaguar's 4.2 litre, 245bhp at 5500rom, in-line six-cylinder, twin overhead cam engine fitted with twin SU carburettors.

It was fitted with Borg-Warner model 8, 3-speed automatic transmission,'Varamatic' power steering, all-round independent suspension and servo assisted disc brakes on all 4 wheels as standard. The limousine had a wheelbase of 11ft 9in. and an overall length of 18ft. 10in. Most body panels were manufactured by Motor Panels and the body was assembled by Park Sheet Metal, Coventry. The bare bodies were then transported to Vanden Plas, Kingsbury, London for painting and final assembly.

The interior of the limousine was finished to a very high standard by Vanden Plas. Extensive use was made of finest walnut veneers in both the front and rear compartments. Leather or West of England cloth covering the seats. Of course in a car of this nature the list of options was endless. One-off orders were welcomed by Vanden Plas. Because of its chassis strength, Vanden Plas were able to continue to offer a 'drive-away' chassis consisting of all running gear, floor structure, front end and roof cantrails to specialised coachbuilders for converting into hearses.

Several DS420s found their way into the UK Royal Household. HM The Queen Mother owned 5 during her lifetime, the first being purchased in May 1970. She did in fact make a personal visit to Vanden Plas, Kingsbury to inspect the car before delivery. It is said that she disliked the double chrome waistline strips which were standard fitment at this time, and had the lower one removed and replaced by a painted red coachline. This change was adopted and became a standard feature of the model in mid 1971.

In mid 1972 a serious design fault with the opening rearmost windows was eliminated. The wind-down window was replaced by a hinged window, which having the bottom sealed, stopped water from entering the rear wing cavity. Not having a window winding handle allowed the rear armrests to be redesigned. Only 2 landaulettes were produced by Vanden Plas in 1973/1974. In 1975 the boot handle was redesigned meaning that the reversing light was moved to under the rear bumper. Other changes included amended bumper overriders in 1976, front panel air intake grilles changed from circular to oblong and front indicator lights changed to oblong in 1979. In 1987 much thicker rubber strip bumpers were added together with a shallower radiator grille. 

After the Vanden Plas factory closed in 1979 production was transferred to Daimler/Jaguar in Coventry where it continued until the last model was produced in 1992.

In total 4,141 DS420 Limousines, of which 2, 480 were finished by Vanden Plas at Kingsbury, and 903 chassis, of which 517 were completed by Vanden Plas, were produced.