The 420 and Soveriegn models were launched in 1966 and sold until 1968 (420) and 1969 (Sovereign) when they were replaced by equivalent Jaguar XJ models. The Mk2 models had spawned the S-type in 1963 with independent rear suspension, enlarged boot, and a choice of 3.4litre engine or the 3.8litre from the E-type. Sales were not as good as expected and the 420 hoped to resolve that by giving the car the 4.2litre engine from the MkX and a front resembling that larger car. Always a stop gap car to keep the Jaguar buyer interested until the XJ6 was available, it also hoped to prepare owners for that new one model car.