Officially the fastest diesel trains in the world, the High-Speed Trains were introduced by British Rail in 1976, operating 125mph services on the Great Western Main Line and the East Coast Main Line before being introduced to other lines later.

When originally built by BREL at Crewe Works, the InterCity 125 units consisting of a pair of Class 43 power units and a rake of Mk3 coaches, were considered to be diesel multiple units and allocated as Class 253 to the Western Region and Class 254 for the Eastern Region, as it was envisaged that the sets would remain in fixed formation. The original Inter-City 125 livery of yellow wrap-around ends, with the Rail Blue design being cut diagonally with grey towards the back of the loco, lasted into the early 1980s.

After an iconic life of service on the East Coast Main Line, LNER removed its Inter-City 125s from service at the end of 2019. To celebrate LNER announced a farewell rail tour. The entire train was repainted in the original blue and yellow livery and the tour lasted for four days.