The APT-E, for Advanced Passenger Train Experimental, was the prototype Advanced Passenger Train tilting train unit. It was powered by gas turbines, the only multiple unit so powered that was used by British Rail. The APT-E consisted of two driving power cars (PC1 and 2) and two trailer cars (TC1 and 2). Each power car was equipped with four Rover-built Leyland 2S/350 gas turbines (and a fifth for auxiliary power supplies), which initially produced 300 HP each but were progressively uprated to 330 HP. Two GEC 253AY nose suspended traction motors provided the traction on the leading bogies. The vehicles were manufactured from aluminium and were approximately 70 ft long (21 m), with articulated bogies between them.

The unit was only intended for testing and was never used in ordinary public service, although it did carry office staff and the occasional dignitary on trial runs. When its period of testing was complete, in June 1976, it was sent to the National Railway Museum, York for preservation. It is now based at the NRM's Locomotion Museum in Shildon.