Rail museum bosses say they are a quarter of the way to saving the Flying Scotsman locomotive for the nation.
A private owner has put the engine up for sale to the highest bidder, who could come from outside the UK.
Two weeks from the deadline for sealed bids, York's National Railway Museum has raised more than £200,000 of the
estimated £1m needed to buy it.
Experts gathered at a London rail yard on Thursday to inspect the engine ahead of the deadline for bids on 2 April.
National Rail Museum head Andrew Scott, who was at Southall Rail Centre for the inspection, told BBC News Online: "I have been amazed at the public support.
"I know now that this is the most famous steam locomotive in the world."
Rail enthusiasts want to save the last engine in its class
At the moment the engine is privately owned by Flying Scotsman Plc and pulls the Venice Simplon Orient Express, which runs out of London's Victoria Station.
Flying Scotsman Plc boss Peter Butler said it was being sold because it did not bring in the returns expected, and plans to build a visitor centre at Edinburgh Waverley fell through.
The 81-year-old engine is a famous world record breaker with a niche in British nostalgia for the steam age.
It was the first to complete the London-Edinburgh run non-stop, and starred in Britain's first talking film.
There are fears the highest bidder for the 'locomotive No4472' could come from abroad.
The NRM says that if it buys the engine, it would run on both mainline and preserved railways. It would also be displayed at railway festivals and in the museum.
Jim Rees, who looks after trains at the NRM, said the Flying Scotsman was unique.
The engine was completely rebuilt in the late 1990s
"If you ask anyone in the street 'Name me a steam engine', they will always have heard of it.
"A big steam engine is the closest thing to a living being that man has invented."
The Flying Scotsman was bought from British Rail in 1963. For 10 years it pulled special trains in the US and was on display in San Francisco before returning to the UK.
The engine, the only surviving one in its class, was completely rebuilt between 1996-1999 and brought back to the mainline.
The NRM has also applied for a grant from the National Heritage Memorial Fund which is being assessed.
Have you travelled on the Flying Scotsman? Send us your memories and comments using the form below.
4472 should remain in this country, it's as simple as that. I have ridden behind her many times and seen her many more times too. She has brought pleasure to countless numbers of people and the prospect of her going abroad permanently is out of the question.
Ian Bowskill, Stotfold, Beds
Sad though it would be if the Scotsman were lost for the country, shouldn't we invest in our current rail system and try to get that working first?
Of course I agree that the Flying Scotsman should remain in Britain. I do have fond memories of the loco's visit to Canada over 30 years ago. For the princely sum of one Canadian dollar, I was able to take a short ride on the footplate during the visit to the Canadian National Exhibition in Toronto.
David Brain, Mississauga, Canada
Golden Days of Steam? My dad was an engineer. Out in the cold mornings to fire up the boiler, constantly adjust this valve and that lever to keep it running, stop every now and then to top up water, back-breaking shovelling of coal, a maximum 8 hours running a day then back to the depot where the fire had to be dumped, everything damped down, hours of cleaning before it all started again the next day.
Be realistic - would you want to do that as a job?
Ah the good old days.
The Scotsman is a charismatic and beautiful piece of machinery but when was the last time most people even thought about it prior to seeing the news article? How many years? So would we miss it if it went abroad? No.
Sorry but, from my perspective, it's the truth
Bob Anderson, Edinburgh
I have no particular love of steam trains but even I can see that the Flying Scotsman is as important to our countries culture as Concord or the 'Madonna with the pinks'. There is no question that it should be saved, what else is the lottery for? - It could go to Swindon though.
Matthew Hawkins, Stroud
Sadly this will undoubtedly go the same way as all other great British inventions - snapped up by the Americans or other countries. We should be proud of our heritage and not sell it to the highest bidder.
As a steam train enthusiast, I would like to see 4472 continue main line excursions in Britain. It would also be nice if Network Rail would allow steam trains to run in Ayrshire, where a local group continually have a hard time getting permission to run trains over a quarter mile long line which is rarely used anyway.
Andrew Thom, Ayr, UK
February 1984 .Coming of the slip road from the Forth Road Bridge I observed hundreds of people on the railway cutting, north of the Forth Bridge . Asking what was going on, I found out that 4472 was coming in about 20 minutes. I sped home for the cameras and returned to find the cutting crowded with hundreds of people waiting for 4472. I got the best photos I have ever taken with the engine going at full pelt towards Inverkiething.
The Government or the lottery should make sure this treasure stays in this country (they've drivelled away millions on irrelevant projects)or why not add a few million on to the price of the Scottish parliament, it wouldn't be noticed. Let future generations appreciate what this country created and have pride in it. This machine is unique.
George Smith, Kelty, Scotland
We MUST keep 4472 in running condition and in the UK. National Treasure is not an exaggeration in this case. Mention Flying Scotsman to any Brit. and they'll know what you're talking about; it set numerous speed records during its operational life; was known from the early days as "The King of Locomotives"; and is the only surviving member of Sir Nigel Gresley's classic 'A3' class of locomotives, the rest having been cut up in breakers yards across the land in the 1960s. Some say "let the Americans buy it, they'll look after it" - well they may not, restrictions on the use of steam locos on US main lines being even more draconian than in the UK. They are just as likely to fill its boiler with concrete and put it on display in a children's playground with a potted plant in its funnel - until rust sends it to the same fate as its brethren.
Bob Evans, High Wycombe, UK
Even if the money were raised to buy the locomotive, would there be the money to maintain it? Any engine of that era needs endless care to keep it running. If a group, anywhere in the world, has the money to do that then it should be given the chance to run it.
The lesson from old trains like the Flying Scotsman should be how extraordinary modern trains are - quiet, clean and faster than any old boiler on wheels - lets celebrate the modern world!
Lewis Graham, Stevenage, UK
When I was a child 4472 used to pass within 400 yards of our house on the way north/ south. It was STUNNING to hear it approach and the noise-steam-power as it whooshed past at full speed as it approached Peterborough was awesome to behold. We need to keep it in the UK. It is an important part of our heritage.
Alan Patterson, Farcet Nr Peterborough Cambs
The A3 Pacifics, along with the GWR 'Kings' stand at the apogee of British steam technology. In the 30's they led the world. We must try and keep as much of our heritage as we can in working order - it isn't the same seeing them stand idle. The awesome impressions of a huge steam engine capable of hauling 15 coach trains at 100mph. are something future generations should be able to experience 'for real'.
Mark Andrews, London
There are too many of these kettles on wheels for the preservation movement to support as it is.
The real question is why the National Railway Museum is not taking proper care of its more recent acquisitions. The gas-turbine Advanced Passenger Train was allowed to get into a terrible state as was electric class 84 and the diesel class 50.
The full historical importance of these exhibits will not become fully apparent for some time, but the NRM only seems interested in dinosaur steam engines.
Mark Drury, Stockport, UK
Its driver let me stand on the footplate of the Flying Scotsman at Edinburgh's Waverley station when I was a small boy in the 1960s. I think the machine was still in mainline service at the time - although not for much longer. It was an impressive experience.
I was later given a Hornby model of the loco as a Xmas present. For people of several generations, the Flying Scotsman was and remains the stand-out icon of a period when British steam technology led the world.
If the opportunity to display the two greatest symbols of British steam rail (Scotsman and Mallard) together at our National Railway Museum in York is not taken and the Scotsman goes abroad, I feel the custodians of our industrial heritage will have let the nation down.
Jim Marshall, York, England
How much did we spend on the Millennium Dome? Methinks we can afford this one easily.
Simon Brookes, Leicester UK
I have only seen the Flying Scotsman once when up at Peak Rail some 2-3 years ago and it pulled the carriages of the restaurant car, it was a great day and the crowds were really unbelievable, this locomotive's attraction is unsurpassed by any other and the need to keep it in Britain for future generations is in the nations best interest, let's not lose something else of our national heritage to Europe
If more than £10m was found earlier this year for an attributed Raphael (the Madonna with the Pinks) so it could remain and give pleasure to many in this country, surely the case for finding money for the Flying Scotsman is just as strong. It gives as much pleasure or more to a different but just as deserving public. Money has to be found for one of this country's most well-known and well-loved objects.
Robert Gardiner, Cambridge, England
My grandfather was one of the drivers of the Flying Scotsman - he used to recount such wonderful stories of this fantastic engine. It would be such a sad day if this national treasure ended up abroad and I know that my grandfather would be fighting its cause if he were still alive today. Keep the Scotsman British!
The government and industry have got together in the past to purchase a 'famous' painting, that doesn't mean a lot to many people, so why is a 'famous' UK-built steam loco legend different? It's a UK treasure so everything must be done to keep it here for everyone to see.
Steve Adams, Sheffield, UK
The days of steam will return! When the electricity and oil run out we'll have to go back to steam in the same way that the end of Concorde meant the end of supersonic flight. The return of steam will be a great day. Let's also get rid of mobile phones, go back to calling a radio a wireless and reinvent the country!
Yes - keep 4472. It's a memory from a time when life was much simpler and better.
Paul Charleton, UK
It's only a train. The history and memories will never fade but spending a disproportionate amount of money on one old engine does not strike me as the best investment of public or even private funds.
Scott, Edinburgh, Scotland
Scott, Edinburgh "its only a train"? Ah but it isn't Scott, that's where you're lack of imagination and passion has failed you. "Only a train" are the anonymous tin boxes that roll into Waverly each day, the flying Scotsman represents the greatest of British Engineering and is BEAUTIFUL. Steam engines have characterises that allow people to feel empathy with them. Logical thinking is the beginning of wisdom Scott, not the end.
Jim Daniels, Surrey "a brute with poor breaks in the wet" has it?! So does my 1949 Riley but it has more charisma in its front bumpers than my brand new BMW has in its entirety. Don't allow the mechanics to blind you to the bigger picture that this is a beautiful graceful old lady that has brought joy to countless people. You would never go to Munich to see her, lets be honest so be glad that there are still many people in this country who would make the effort to see the engine if she remains in this great country. How do you feel the engine drivers feel about their lives driving the modern trains of today by the way?! Do you think it makes them proud?
By keeping the engine in this country, we celebrate and appreciate the great engineers who designed and built this amazing steam engine.
Jamie Young, Edinburgh
The Flying Scotsman is a national treasure and as such should be part of the National Collection in the National Railway Museum.
The 4472 was the very first steam engine I saw back in about 1973, aged 3 my Dad took me through the corridor in the locomotive's tender which was used for crews to change without the need to stop the train. This allowed non-stop running between Kings Cross and Edinburgh.
The Government must refuse an export licence if the UK bid fails. Yes I am a railway enthusiast and yes I am biased!
Steve Osgood, Flitwick, UK
This is part of our heritage and should not be sold off to overseas buyers. It's about time the National lottery starting putting money into projects protecting our heritage for future generations.
This should be in a working museum in the UK!
Ian, Bristol, UK
Unfortunately we haven't been able to travel on the 4472. For my dad's 60th birthday I bought him tickets to travel on it but they changed the departure times of the train and he missed out. Dad works on the railway and because he has to travel to different incidents at the drop of a hat he is called 4472 - with him being Scottish to its an apt name. The engine should stay in the UK and I fully support the appeal that the NRM is running. I shall be sending my donation shortly.
Heather Fyfe, Harlow, England
As a boy, I remember my father taking me to Sundon, Bedfordshire to see the last British Railways scheduled service of the Flying Scotsman fly past. After that, sadly, it became a rare occasion to see a steam train on a main line run.
Bruce Thomas, Venlo, The Netherlands
I was lucky enough to travel from London to York on the footplate of the Flying Scotsman when it had been bought by Alan Pegler, who was a friend of my parents. Mr Pegler used to run it between London and York with train enthusiasts on board as a private thing. It was very, very exciting and ever since then I have had a soft spot for the train and always read about its news! I DO hope it can be kept in this country - it really should be, but if not at least the Americans (who will presumably get it eventually) have the resources to look after it as it deserves!
Carolyn Tate, London
I have driven the Flying Scotsman. A brute with poor braking characteristics in the wet.
I am not so full of nostalgia that I feel a need to keep it in the UK.
Travel is so cheap nowadays that it possibly would be cheaper for me to visit it in Munich rather than going to York
Jim Daniels, Chobham Woking Surrey
Although 4472 has never been a real favourite of mine it is sad that the locomotive was excluded from the official list of engines drawn up for preservation as part of the National Collection. This was due to the prevailing criteria at the time and unfortunately Flying Scotsman could not be included. For the same reason L.M.S.R. No. 6100 Royal Scot was left out and fortunately private individuals had the will to save both engines for the nation even if it was for other reasons at the time. However time has moved on and attitudes have changed from the 1960s when it was the fashion to obliterate anything deemed to be old fashioned. It is vital that this locomotive, part of our National Heritage, should remain in this country, and the only appropriate custodian is indeed the National Railway Museum. I cannot share the views of Jim Daniels. Perhaps he hasn't the aptitude for driving steam locomotives.
John Bennett., Whaley Bridge, Derbyshire, England.
April 27, 1994 - the day my first son was born and the day my wife's former company floated on the stock market. Why is that relevant? The company was Oxford Molecular, and the man who announced both events at the meeting in the pub that evening was Tony Marchington - he went on to buy the Flying Scotsman and arrange for the most expensive steam engine restoration in history.
4472 is a part of Britain's heritage. Anyone who has seen it steaming across the viaducts on the East Coast Main Line can hardly doubt this. I would be greatly saddened if 4472 did not remain in running order, and run on the main line at least sometimes.
Guy Chapman, Reading, UK
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