The Inter-City 125 was the brand name of British Rail's High Speed Train (HST) fleet, which was built from 1975 to 1982 and was introduced into service in 1976. The Inter-City 125 train is made up of two Class 43 power cars, one at each end of a set of carriages (the number of carriages varies by operator). The train operates at speeds of up to 125mph in regular service, making it the fastest diesel-powered train in the world, a record it has held from its introduction to the present day. After four decades, most of the HST fleet is still in front-line service, with various UK train operators.

This fascinating Manual looks at the evolution and anatomy of the Inter-City 125, along with details of the operation and servicing of the trains, views from drivers, and details of how the trains were modernised for the 21st century.