Image caption Bittern is one of the six surviving locos designed by Sir Nigel Gresley

A 1937 steam locomotive has run along the section of track where a another locomotive set an unbeaten world record 75 years ago.

Bittern, an A4-class engine, a contemporary of Mallard, the world's fastest steam locomotive, set off from King's Cross station for York.

Mallard set a record speed of 126mph near Grantham on 3 July 1938, which remains unbeaten to this day.

Up to 250 people were on board the train, which reached 92.8mph.

It had been given special permission by authorities for the run to exceed the 75mph limit for steam trains.

Steam locomotives were phased out in the late 1960s.

Bittern set off from platform four at King's Cross, stopping at Potters Bar in Hertfordshire, to pick up more passengers.

Richard Corser, general manager at organiser Locomotive Services Ltd, said: "Today is the culmination of a lot of months of preparation to make this happen, to go at a high speed and to give the passengers a bit of a flavour of what high-speed steam was like.

"This country's very famous for its engineering skills and steam was its cradle."

Bittern and Mallard are two of 35 A4s designed by engineer Sir Nigel Gresley, but only six survive.

The surviving locomotives will be reunited at the National Railway Museum in York to celebrate the 75th anniversary of Mallard's record on 3 July.

Dominion of Canada was shipped from Montreal last October while Dwight D Eisenhower has reached York from the US and both have been restored for the anniversary.

Union of South Africa and the Sir Nigel Gresley will also join them at the museum.

Anthony Coulls, the museum's senior curator of rail vehicle collections, said: "What we're planning is a major celebration - people will be coming from four corners of the Earth.

"The gathering of the six locomotives is the jewel in the crown."