Sir Richard Branson wants the Flying Scotsman to stay in the UK

The offer includes more than �425,000 raised through a public appeal and a substantial donation from Sir Richard Branson on behalf of the Virgin Group.

The locomotive's owner, Flying Scotsman Plc, put it up for sale in January and the bidding process ends on 2 April.

The future of the Doncaster-built loco is expected to be announced next week.

Andrew Scott, Head of the National Railway Museum in York, said the organisation had received a "staggering" amount of public support for its bid to keep the Flying Scotsman in the UK.

"There can be no doubt that without the generous donations and goodwill of the British public, we could not even have hoped to put together a worthwhile bid," he said.

"We remain as optimistic as ever that the National Railway Museum will at last be able to provide a secure future for Flying Scotsman."

Mainline operation

The Flying Scotsman was put up for sale after plans to build a visitor centre in Edinburgh to house it fell through.

Following the retirement of Concorde last year, Virgin boss Richard Branson said he was determined to see the Flying Scotsman stay in use.

The size of his donation has not been disclosed.

Staff at the museum in York have handled more than 5,500 calls, letters and e-mails from the public since the appeal was launched.

If the bid is successful, donations received after 1 April will be used to ensure the locomotive is fit for mainline operation.

Mr Scott said that the museum hoped to have the historic locomotive as a centrepiece for its Railfest celebrations to mark the 200th anniversary of the train in May.