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), these 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, approx with articulated bogies between them.