Mini
Alec Issigonis, the designer of the Morris Minor, came up with the Morris Mini Minor (or Austin Seven) as it was initially called, which broke ground in so many ways with a front mounted transverse engine in unit with the gearbox, driving the front wheels in a car that could carry 4 adults, yet was 30% shorter than a Volkswagen Beetle. Launched in early 1959 it became a sensation, sold under either the Austin or Morris brand. John Cooper got to work on a Mini straight away, increasing the engines capacity from 848cc to 997cc which with its twin carburettors and other tweaks increased the standard 34bhp engine to 56bhp. Cars were made in various specifications until 1971, with the Clubman and Clubman 1275GT up to 1980. And for 1990 in 3 formats - standard , Cooper and Cabriolet.
Let's not forget the other BMC variations on the Mini theme. The Riley Elf which was supplied with a detuned 998cc Cooper engine (giving 39 bhp rather than the Coopers 56bhp) and the virtually identical Wolseley Hornet, both in production from 1961 to 1969. These 2 cars had the advantage of a 50% bigger boot space.