The Mallard, designed by Sir Nigel Gresley, is on display in York
A railway expert has said a steam locomotive speed record set 70 years ago will probably never be broken.
The Mallard steam locomotive reached 126 miles an hour on a stretch of track near Grantham in July 1938.
The world record was set in a train designed by Derbyshire engineer Sir Nigel Gresley.
National Railway Museum spokesman Bob Gwynne said a modern steam engine might reach that speed, but it would probably "not be allowed to" for safety reasons.
"The record may stand for all time because it takes a great degree of courage to drive a big mechancial machine of this size - over 100 tonnes - at that speed."
"It might be possible but unlikely," he added.
'Rocking and rolling'
The locomotive operated on the East Coast Mainline route from the late 1930s until the 1960s.
"Gresley's masterpiece was a world-beating design," Mr Gwynne said.
Ken Willetts, a fireman who worked on the Mallard in the 1950s, said: "Everyone wanted to work on the fastest locomotive in the world - it was a piece of history.
"I didn't ride on it at 126 mph, but I did many times at more than 100 mph."
The York-based museum's engineer Richard Gibbon said that on the day the record was broken, the Mallard was "in perfect condition and only five months old".
He described the wooden "speed-recording" carriage on the train as "rocking and rolling" and how crockery was knocked off shelves when the record was set.
The museum plans to reunite the Mallard with three other "A4" locomotives - the Bittern, Sir Nigel Gresley and Union of South Africa - on 5 July.
The museum's in-house theatre troupe will also mark the anniversary with a "recreation" of the moment driver Joseph Duddington and fireman Tommy Bray reached 126mph on the downwards slope of Stoke Bank near Grantham.
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