THEY have powered their way through Brunel’s heartland since the 1970s, notching up thousands of miles in the process to become an icon of British engineering.

And today the High Speed Train Inter-City 125 marked its 40th anniversary at London Paddington station following a weekend of celebrations at the National Railway Museum in York.

The launch of the first HST passenger services running between London, Bristol and South Wales was on October 4, 1976.

The train’s introduction revolutionised Britain’s railways and economy. Not only did the locomotive set new standards in comfort but it radically reduced journey times, consequently becoming a record breaking design icon.

To date the HST remains the fastest diesel train in the world operating on conventional track and at a fraction of the cost.

Forty years on and Great Western Railway still has a 58-strong fleet of HST sets that make their way from London down to the furthest reaches of the mainline in Cornwall to Penzance.

To mark this milestone anniversary the rail operator partnered with the National Railway Museum in York to present the original HST Class 43 power car in all its now restored glory, as it would have been seen for the first time in 1976.

The GWR HST Class 43 power car (43002) was earlier this year aptly named after Sir Kenneth Grange in honour of his creation of its exterior styling of the power car nose cone, interior layout of the HST, and the train’s aerodynamics.

The industrial designer himself was at the museum for a plaque giving ceremony.

Also on display in the South Yard was another GWR Class 43 power car (43185) which made its first public appearance having recently been repainted in the Intercity Swallow livery first seen in 1988.

Andrew McLean, head curator at the National Railway Museum, said: “The introduction of the HST greatly improved the economies of the towns and cities that it served and made commuting from large distances possible. Its success is such that it still looks stylish, still carries large numbers of passengers at 125mph and remains vital to keep Britain moving.

“It stands as testimony to the excellence of British rail engineering and the genius of the industrial designer Kenneth Grange who created its iconic shape.

"Simply put, it is arguably the most successful train the world has seen and we’re delighted to be able to celebrate it at the museum.

"The ceremony introducing the new power car will commemorate the excellence in design but also inspire future generations of train engineers and designers.”

GWR engineering director Andrew Mellors added: “We’re delighted to be able to present to the public the power car named after Sir Kenneth Grange and also to welcome him to the museum for the unveiling at the home of locomotives, the National Railway Museum.

“With a brand new fleet and the very latest in train design, the Intercity Express Train, due onto the Great Western network next summer, it is an opportune moment to remember an icon that has served the industry so well.

"The longevity and success of the HST is a testament not only to those who designed and engineered it, but also to the many who have maintained them.”