The prototype was eventually tried out on the Great Western Main Line, and achieved a new British railway speed record when on 10 August 1975 it hit 152.3 mph (245.1 km/h)[3] whilst on test with the Western Region between Swindon and Reading.

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.

The APT-POP (Power-0-Power) set was a rake of three skeletal unpowered carriages used as a test bed for the suspension, tilting and braking systems used by APT units.

The 'Power pumps' were only mock-ups, though similar externally to PC1 and PC2 in the APT-E unit minus cabs, and the whole set had to be hauled by a locomotive.