STANDING more than 13ft tall, the huge metal skeleton towers above the volunteers who scuttle around, devoting their time and painstaking effort to trying to coax it into life. Even though it is just over half completed, and with its vital moving parts, including the boiler, still to come, it already has the shape of a steam locomotive.

The A1 Pacific Tornado was to be the pride and joy of rail enthusiasts across the country. The first new steam locomotive to be built in Britain for more than 40 years, proof that the seemingly impossible could come true and leading the way for the rebirth of the giants of steam.

But now, as the frame sits in the Hopetown engineering works in Darlington, there are signs of serious dissent in the project for the first time in its ten year history. About 100 of the 1,500 covenantors - who provide much of the money to build the locomotive - turned up for a meeting earlier this month after doubts were raised over the quality of some of the work completed so far.

Now a clear split has emerged, between the trust who are running the project and a disaffected group of covenantors, who believe substantial engineering errors have been made which require costly corrective work. Each side is talking about legal action, the trust to find out how the rebels got hold of the names and addresses of covenantors, and the rebels to try and stop the trust covering up their mistakes. It all seems an unfortunate turn for a project which had seemed to be going so well.

And, what is worse for enthusiasts nationwide, the trouble comes after a previous attempt to capitalise on Darlington's illustrious heritage as the birthplace of the railways ended in disaster. The plug was pulled on the planned Cavalcade of Steam, to celebrate the 175th anniversary of the Stockton and Darlington railway, just weeks before it was due to take place last August.

Organisers blamed the decision of a major investor to pull out but when the smoke cleared from the wreckage, it emerged they had run up debts of £750,000. And the owners of many of the locomotives due to take part had never even been contacted, to see if their engines were available.

One common thread was David Champion, Rail 2000 chairman and chairman of the A1 Steam Locomotive Trust until earlier this year, when he stepped aside for personal reasons.

But for Robin Jones, editor of Heritage Railway magazine, the difficulties facing the Tornado do not seem enough to see this project suffer the same fate as the Cavalcade of Steam.

"It seems that somebody has produced a part for the Tornado which has been questioned, and the trust is in talks to get it rectified," he says. "The difference between this and Rail 2000 is that with Rail 2000 the fog shrouded it right to the end.

"None of the railway magazines, who knew that engines had not been booked to take part in Rail 2000, wanted to speak up. They believed the first person to say the project was going wrong would be blamed for it going wrong.

"There were rumblings about Rail 2000 for six months before, that it was not going ahead. With the A1 Tornado, I think it is a glitch that has taken some time to sort out. It is a fault that can be rectified without setting the completion date back ."

He says the trust had been open with the covenantors by admitting that problems existed, but these difficulties were a drop in the ocean when set against the total £1.7m cost of the project. But, he says, the significance of the Tornado should not be underestimated.

"It is too important for railway heritage to let this fail. Rail 2000 was a one-off, but if this project fails it is unlikely there will be further new build of standard gauge steam locomotives. That might mean nothing to the ordinary man, but it means heritage railways could grind to a halt in the future.

"But if it is successful, and it works and pays its way, people might be more forthcoming with sponsorship and bank loans for other projects."

With about ten million journeys on steam locomotives every year, railway heritage is now a big industry, with the North York Moors Railway one of the most successful in the country. But restored railways have also had their fair share of internal squabbles.

For Colin Divall, professor of railway studies at York University, the difficulties may be inherent in any voluntary project run by enthusiasts. "When people are doing things for nothing, and it is what they want to do, it can be difficult to get people to agree on what the overall aim of the project should be," he says.

"If you look at the history of railway preservation, which goes back 50 years or so there have been occasions when projects have either foundered or faced great difficulties, and, in that sense, both Rail 2000 and the A1 are part of that history of problems. There are also projects which have had difficult times and have pulled through and are now some of the most successful. Generally speaking, these differences are patched up."

But if Tornado's difficulties do turn out to be terminal, it will be a another blow to Darlington's reputation, according to Barrie Lamb, chairman of the town's Railway Preservation Society. Although the society is aiming to restore its own locomotive, a Standard 78018 built in the town in 1953, he is keen to see the A1 project succeed.

"Darlington's railway heritage is probably the most important thing for the town, and we get a lot of people from all over the country coming here for that reason," he says.

"The bad publicity from Rail 2000 stuck a little bit to Darlington, and it was unfortunate that it seemed to be badly planned. I don't think that, as a town, we realise the assets we have got at times and we do take it a bit for granted. It is a shame this is happening with the Tornado, because I don't want it to give Darlington a bad name."

An independent inspection on work completed on the Tornado so far is due to take place next month, which should at least determine whether doubts raised by the rebel covenantors were justified. But Robin Jones is confident the project has a future.

"I think this is a storm that will be weathered. I see no reason to believe this project won't succeed in a big way, and I believe it will put Darlington on the world engineering map again," he says.

Steam railway enthusiasts across the country will be hoping he is right, and that the Hopetown works does not turn out to be the Tornado's graveyard.