The Mk 1 was presented to the public at the
London Motor Show in October 1963, and volume sales began in January 1964. Continuing in production until 1969, this version came in
saloon and, from 1965,
estate forms. The estate car body shell was partly built by
Carbodies, and in the Mk 1 version was the same length as the saloon. Various minor improvements were made during the period of which the most noteworthy, probably, was a significant upgrade in October 1966 to the "previously rather ineffective" ventilation, with eyeball vents added in the centre of the facia and the heater controls repositioned beneath them. In October 1968 the 2.5 PI (petrol injection) Mk 1 was launched, fitted with a
Lucas Automotive mechanical
fuel injection system. Performance was very good, but the PI models (along with the TR6 models) gained a reputation for unreliability and poor
fuel economy. In Australia, these models suffered badly because of the summer heat. The electric fuel pump commonly overheated causing fuel to vaporise and render the engine inoperable until the pump cooled down. The overheating of the pump was caused by a combination of very high pressure fuel loads (over ) and a pump that was adapted from what was originally a windscreen wiper motor. As such, it did not cope well with sustained pressures in moderate to high ambient temperatures. Because of the launch late in the Mk I's life, there are relatively few PIs in the original shape. File:Triumph Estate (2368440169).jpg|Triumph 2000 (Mk 1) Estate File:Triumph 2.5 PI.jpg|Triumph 2.5 PI Mk 1 Saloon == Triumph 2000 Mk 2, 2.5 PI Mk 2, 2500TC and 2500S ==