High speed rail travel finally reached the UK on this day in 1976 as British Rail launched its new 125mph engine, dubbed the Inter-City 125.

Powered by two diesel motors, each giving an output of 2250bhp, the new engines were found to be capable of 148mph in testing, making them the fastest diesel-powered trains in the world – a record they still hold today.

A high speed train (HST) had first been proposed in the late 1950s as British Rail sought to counter the growing popularity of motorways. As the government was unwilling to fund new rail networks, the development of increasing existing line speeds was prioritised.

Until the arrival of the 125, a speed limit of 100mph was in place on British railway lines.  The 25% increase in speed and ability to rapidly increase or decrease acceleration made the new engines ideal for passenger services.

[Read more: March 27, 1963: Beeching's axe changes the face of Britain's railways forever]

The first 125s to be introduced provided high speed journeys between London, Bristol and Cardiff. They were the first rolling stock to have aircraft-style seating, and served hot food “with the aid of a state-of-the-art microwave oven”, according to the BBC.

By the start of May 1977, 27 of the 125 engines were in service on the Western Region, completely replacing locomotives on the Bristol and South Wales routes, and increasing passenger volumes on the services thanks to their speed and frequency.

As well as bringing considerable improvement to UK railway services, the success of the 125 ushered in a period of confidence for British Rail, epitomised by their marketing campaign which buoyantly affirmed: “This is the age of the train”.