THE expected date to get historic steam locomotive Flying Scotsman back on the rails has been delayed until next year, National Railway Museum bosses said today.

The effort to get the train back into use was predicted for this year, but has been put off until summer 2011 because of a series of issues that occurred during the restoration process.

Flying Scotsman is currently based at the National Railway Museum (NRM) workshop in York, North Yorkshire, where a team of engineers are working to bring it back to its original best.

Last year, the NRM launched the Steam Our Scotsman appeal with the aim of raising £250,000 to get the famous 4472 train, which was designed by Sir Nigel Gresley and built at Doncaster works in 1923, back on the tracks.

So far just over £140,000 has been raised and work is ongoing.

Helen Ashby, NRM head of knowledge and communications, said problems during work on Flying Scotsman pushed timetabling off course.

"There's been a series of issues," she said. "Some of the components that we've now had the opportunity to strip and check ready for replacement we've found to be more worn than we anticipated.

"It's been a lot more replacement and refurbishment work than we thought there would be originally."

She said to get the train tested in spring 2011 and fully in use by the summer of that year was a more realistic programme as almost all components had now been investigated.

Chris Beet, engineering and rail operations manager, said there had been a series of surprises along the way as work progressed.

He said: "Essentially it's a very big job and very time consuming.

"If you make a mistake with a very expensive piece of material then you've wasted your material and youve got a big time delay."

But he said once Flying Scotsman was back in full working order, the sense of achievement would be huge.

"It should have been scrapped 46 years ago by British Railways," he said. "It's been running longer now in preservation than it actually was when it was built.

"It's a tremendous challenge, but it'll be a real achievement for the workshop staff, the museum and for British industry that we can still do work like this 80-odd years after it was first built."