The locomotive has spent 12 years on Swanage Railway's track

The 128-tonne locomotive, "257 Squadron", will arrive at the grounds of the Great Dorset Steam Fair by road transporter on Tuesday.

Fundraisers from Swanage Railway hope to raise �100,000 towards the overhaul of the locomotive's massive boiler.

It is hoped visitors to the Tarrant Hinton event will donate to the scheme.

257 Squadron is a smashing locomotive and one of the best designs of steam locomotive ever built Swanage Railway volunteer Mick Hatton

The arrival of the Battle of Britain-class Bulleid Pacific No 34072 will be watched by 81-year-old veteran Bournemouth steam locomotive driver Stan Symes, who himself has driven 110 different classes of steam locomotive.

After visiting the show - which begins on 1 September - the locomotive will continue its road journey to Kent where it is to be given the major overhaul before returning to Swanage Railway.

Fundraising officer Alan Maynard said: "We need to raise the money needed to give her an overhaul as soon as possible so that 257 Squadron can again run on the Swanage Railway and continue to give pleasure to hundreds of thousands of people.

"The overhaul will be a major engineering job and we'd love to get the locomotive back in service by 2008 but we do need the public's support and 257 Squadron's appearance at the Great Dorset Steam Fair is part of that."

'Spam can'

The locomotive was built at Brighton in 1948 and named after the Royal Air Force squadron based at Warmwell, near Dorchester, that fought in the Battle of Britain.

257 Squadron spent its career hauling express trains across the south of England until it was withdrawn in 1964.

After being restored from the 20 years of decay it spent in a Welsh scrap yard, the locomotive went on to enjoy 12 years hauling trains on Swanage Railway's rebuilt six-mile Purbeck line.

Volunteer Swanage Railway fireman Mick Hatton said: "257 Squadron is a smashing locomotive and one of the best designs of steam locomotive ever built with its then futuristic air-smoothed casing which caused it to be dubbed a "Spam can" when it was built at Brighton in April, 1948.