Based on the pre-war 1.5L, 2.5L and 3.5L models, the Jaguar MK.IV was introduced in 1946. After the war, the name SS could no longer be used and the cars became known simply as Jaguar.
Although commonly known as MK.IV, this was never a name officially given to this model but has been used as a term of reference for those cars produced immediately after the war.