The Class 370 tilting trains, also referred to as APT-P (meaning Advanced Passenger Train Prototype), were the pre-production Advanced Passenger Train units. Unlike the earlier experimental gas-turbine APT-E unit, these units were powered by 25kV AC overhead electrification and were used on the West Coast Main Line between London Euston and Glasgow Central. However, due to ongoing technical problems with these pre-production units, and a lack of cash or political will to to take the project forward, the planned APT-S production series units were never built.

Units were numbered 370001-370006 (plus a spare driving car labelled 370007) were formed as follows:

48101-48107 - Driving Trailer Second
48201-48206 - Trailer Second
48401-48406 - Trailer Restaurant Second Buffet
48301-48306 - Trailer Unclassified
48501-48506 - Trailer First
48601-48606 - Trailer Brake First
49001-49006 - Motor

A full train was made up of two units running back-to-back, with the two motor cars adjoining. The motor cars had no seating accommodation, or a through gangway, so the two halves of the train were unconnected for passengers. All six units were withdrawn during 1985-86, and most cars were quickly scrapped. Only a handful of cars have survived; 49006 is at the National Railway Museum's Locomotion annexe in Shildon, while 48103/48404/48603/49002/48602/48106 are at the Railway Age , Crewe.