PLANS to get one of the world's most famous locomotives back on the tracks have hit the buffers - temporarily at least.

After a painstaking restoration programme the legendary Flying Scotsman had been due to go through steam tests and commissioning runs later this month.

But the project has been unavoidably delayed and more work is now necessary - after cracks were found in the chassis of the iconic loco.

Now the steam tests are unlikely to be carried out until autumn and she will go on show at the National Railway Museum in York much later than August, as was originally planned.

And at this stage it is not possible for the museum to confirm when the engine - No 4472 - will be able to operate the passenger journeys that are so eagerly awaited.

After the cracks were discovered engineers at the museum's workshops carried out an extensive examination to identify the extent of the problem.

It was quickly established that the locomotive required essential remedial work, which will be carried out in the next two weeks..

The repairs should ensure the locomotive continues to meet the high standards of work that have been employed throughout the project and that once it is complete she should be able to run for decades to come.

Museum director Steve Davies said the development had been a very disappointing one.

He added: "It is important for our visitors to understand that the reason for the delay is because our workshop team are doing everything they can to ensure the remedial work taking place matches up to the meticulous approach that has been taken on the restoration project from the very beginning."

He added: "The completed locomotive they will see later this year will be restored to the highest quality and our visitors can rest assured that the safety of the locomotive and its future passengers has been of utmost importance throughout the project."

The Flying Scotsman was built in Doncaster vin 1923 and was saved for the nation by the museum back in 2004 when it raised some £2m in a huge nationwide appeal.

Her ambitious restoration has been supported by Tata Steel, formerly Corus, a £275,000 grant from the Heritage Lottery Fund and support from many other organisations.

Details of display dates and ticket sales will be published as soon as they can be confirmed via the website nrm.org.uk/flyingscotsman