As early as 1955, when the Triumph TR3 had just been launched as the successor to the TR2, the manufacturer was already thinking about its successor. The TR4 was not presented until 1961, but in between interesting prototypes, fast racing cars and some special models were produced that have almost been forgotten. This report looks back on the period from 1955 to 1961 and tells part of the development history of the Triumph TR4, illustrated with photos that have never been shown before.