On the inside the most obvious change was the newly designed seats, which replaced the ‘bucket’ style ones used in the 3.8-litre models. Externally the only change was the addition of ‘E-Type’ and ‘4.2’ badges to the boot lid – all 3.8 models simply carried a ‘Jaguar’ badge. A 2+2 model was introduced in September 1965, due to popular public demand, with a lengthened a wheelbase and a raised roof to make room for the addition of two small rear seats

There were detailed changes throughout the model life; the most noticeable arrived in late 1967 when the glass headlight covers were deleted at Roadster Chassis No.864 for RHD models and Chassis No.5889 for the LHD models. Although there was never a change in model type designation, these open headlight Series 1s have been retrospectively given the ‘Series 1½’ moniker.

Most RHD examples kept the Series 1 interior but, as parts came on-stream for the soon-to-be introduced Series 2 model, items such as the altered dash, rocker switches and redesigned door handles began to be introduced. By then US-bound examples were also fitted with twin Stromberg carburettors which reduced power considerably. Most US examples were also fitted with a 3.54 final drive ratio throughout the 4.2 production run, compared with the 3.07 ratio for European and home market cars. As a result these examples can feel quite busy, although top gear acceleration is naturally improved.