For the East Coast Main Line modernisation and electrification programme, British Rail needed a new passenger train that could offer services between King's Cross and Edinburgh with a top speed in excess of 125 mph (201 km/h). With the failure of the APT-P programme, the new plan was to develop a more conventional, loco-hauled trainset. It got the name “InterCity 225” due to the projected top speed of 225 km/h or 140 mph. Many technical features of the APT-P were to be integrated into the new train.

The locomotive for this train would be known as class 91 and was nicknamed “Electra”. It has four axles and an asymmetrical body with the main cab in the aerodynamic nose and an auxiliary cab in the blunt end. All four traction motors are mounted in the body and connected to the axles via cardan shafts. Unlike other electric locomotives built at that time, they do not have three-phase AC traction motors and deliver a relatively modest output of 4,700 kW.

31 locomotives of the class 91 were built by BREL at Crewe between 1988 and 1991. A total of 314 Mark 4 passenger carriages and 32 matching Driving Van Trailers (DVTs) were built to complete the train sets. All were designed for a speed of 140 mph, but safety concerns due to missing in-cab signalling equipment meant that they are only being operated at 125 mph. Additionally, tilting technology did not make it into the new train.

In this configuration, they did not much advantage compared to the diesel-powered HST. They had better acceleration, but this did not have much advantage on long runs with few stops. Nevertheless, 91010 set a record for the fastest British locomotive in September 1989 with 161.7 mph or 260.2 km/h. After privatisation, they came to Eversholt Rail Group which leased them to different operators over the years. Between 2000 and 2003, they were refitted by Adtranz to improve the reliability of their electric part. Since 2021, 13 have been scrapped and several have been stored.