The Jaguar S-Type wad produced from 1963 to 1968. It was a technically more sophisticated development of the Mk II, offering buyers a more luxurious alternative without the size and expense of the Mark X. The S-Type sold alongside the Mark 2, as well as the Jaguar 420 following its release in 1966.
The S-Type was a major redevelopment of the Mark 2. It used a mid-scale version of the Mark X independent rear suspension to replace the Mark 2's live rear axle and featured longer rear bodywork, among other styling and interior changes. The S-Type was available with either 3.4 or 3.8-litre XK engines but only in twin carburettor form because the triple carburettor setup would not fit into what was essentially still the Mark 2 engine bay.
By the time of the S-Type's release in 1963, the Mark 2 remained an unexpectedly strong seller despite its age. Although the Mark X was selling less well than hoped, especially in its intended market of the USA, Sir William decided to retain all three models in the Jaguar range concurrently. The Mark X was renamed "420G" in 1966 and was joined by another new model, the 4.2-litre 420. The 420 was developed to replace the S-Type but because some demand remained for the S-Type, all four saloon models (Mark 2, S-Type, 420 and 420G) remained on sale until the arrival of the XJ6 in 1968. The XJ6 replaced all but the 420G in the Jaguar range.