HORNBY BR, Class Advanced Passenger Train, 5-car Pack, Grey

The British Rail Class 370 Advanced Passenger Train 5-car Pack Set 370 003 comprises DTS Sc48103, TBF Sc48603, and NDM Sc49003 City of Derby, along with Set 370 004 comprising TBF Sc48604 and DTS Sc48104. By 1970, the British Rail Board had begun considering the third design phase of the Advanced Passenger Train, with the prototype for the full production trains set to incorporate the technology of the APT-E in a practical application. The pre-production APT project, or APT-P, was initially considered a proving prototype for evaluation, prior to the finalised Advance Passenger Train design being authorised for squadron service, known as the APT-S.

The decision to use electric traction for the production APT led to the West Coast main line between Euston and Glasgow as the obvious route for conducting testing, as it was electrified along its length and featured some severe curves that curtailed high-speed travel. The target commencement of services was set for 1977, and the Chief Mechanical and Electrical Engineers' Department (CM&EE) design engineers began work in October 1973. The passenger business of British Rail decided upon the original configuration for the APT-P, with each set comprising fourteen cars and the two power cars marshalled at the outer ends of the sets.

However, it soon became clear that the use of two pantographs, one on each power car, was unsuitable for the OHP wires in place at the time, and the use of two power cars in the middle of the train became the only option, effectively cutting the train in half. This created two 1+6 formations of DTS, TS, TRBS, TU, TF, TBF and NDM (Non-Driving Motor), through which passengers could not pass due to the high magnetic fields generated by the electrical equipment contained in the NDM.

The NDM was the first vehicle completed for testing in June 1977, spending a year on static tests at RTC Derby and dynamic tests on the WCML with a spare HST Power Car from September 1977. In mid-1978, the power car was joined by the rest of the first half set for testing on the WCML, and the full train was unveiled to the press on June 7th, but industrial action delayed the commencement of various formations testing until February 1979.

On December 20, 1979, a new rail speed record of 162.2mph was achieved, and by March 1980, all three APT-P trains were delivered and ready for mileage accumulation on the WCML. With testing indicating that all was progressing to plan, shadow passenger service was set to commence on June 9, 1980, with a daily Glasgow/London return service. However, a derailment caused by a faulty articulated bogie during a demonstration run on April 18th with a 1+9 set signalled the beginning of the APT 'jinx' and the postponement of passenger introduction.

Wheelsets had to be rebuilt across the fleet, and reliability problems with the tilt, transmission, and braking systems were also exacerbated by the mediocre ride quality. It was also found that failure of the tilting mechanism could result in the APT exceeding its kinematic envelope and potentially coming into contact with an APT travelling in the opposite direction. It was not until Spring 1981 that main line testing could resume, by which time media and public opinion had turned against the project, with some individuals in Government and within the British Railways Board expressing their discontent.

Entering public service on December 7, 1981, the APT initially performed well, but very cold weather in Scotland on December 9th and again on December 11th resulted in the brakes freezing, leading to the APT being taken out of traffic until the summer of 1982. A year of technical R&D project running followed, before limited passenger running took place across 1983/84 to assess passenger comfort using the full 2+12 sets between London Euston and Glasgow, culminating in a new time and speed record for the 401 mile trip of three hours and fifty-two minutes; an average speed of 103mph.

Despite exceeding its budget, the APT-P had now effectively reached the end of its development programme, and although a number of plans had been suggested for the implementation of APT in service, in a number of formations and with varying traction options, the APT-S, APT-R, APT-T, APT-U and APT-V projects never materialized. The fleet of six sets had been reduced since March 1983, with parts being cannibalised to keep the remaining vehicles running, and at the end of May 1985, the APT-P was withdrawn from service, with the Intercity Development Train (APT-D) continuing until December 1986.

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