Announced in 1967 the APT project, developed to reduce travel time while using existing 130 year old track alignments, was first demonstrated in 1975 by the gas turbine powered experimental unit APT-E. Important new features included the much publicised tilting bodywork, which gave a more comfortable ride on curves at speeds up to 155 mph, and hydro-kinetic brakes, which made APT compatible with existing signalling by maintaining stopping distances at those of ordinary trains.
Three prototype electrically powered trains were built at Derby, the passenger cars articulated on one shared bogie at each end. Two power cars at the centre of the 14 car trains each developed 4,000 HP (2,980 kW).
The prototypes were based at Glasgow's Shields Electric Traction Depot and during trials in December 1979 APT-1 raised the speed record on a British railway to 160 mph (257 km/h) near Lockerbie.
The trains entered service in December 1981, ran test and relief services for five years and successfully proved the principles of active suspension.