Thousands of people are expected to flock to West Norfolk train stations tomorrow to see a hissing mechanical marvel steam its way to London.

The Gresley Pacific Sir Nigel Gresley 60007 locomotive will roar into life at 9.54am when it leaves King's Lynn train station before chugging its way through the Fens.

After picking up passengers at Downham Market, Ely and Cambridge, the special service will then join the East Coast Main Line at Hitchin and is expected to arrive at London King's Cross at 12.30pm.

Some of the 300 passengers on board will also enjoy a full English breakfast as the locomotive glides through the picturesque countryside.

Passengers will then enjoy the sights of the captial before the service - which has been organised by Lynn-based Railway Touring Company - will leave the London train station at 6.33pm to return to Norfolk.

A three-course Christmas dinner will be served on the return journey to Premier Dining passengers - which costs �139 for adults and �99 for juniors.

Nigel Dobbing, managing director at the company, said the train is scheduled to return to Cambridge at 7.41pm before pulling in at Downham Market at 8.20pm, Watlington at 8.28pm and finally King's Lynn at 8.44pm.

He said: 'People coming along to see the steam train sat in the station will think they have been transported back in time.

'It is the first steam train to leave King's Lynn for almost two years and there has been quite a bit of excitement about this special event.

'For the passengers it will be a completely different experience compared to today's trains and for those watching from the station platforms it will be a spectacle to treasure.'

The Sir Nigel Gresley locomotive was built in 1937 by the London and North Eastern Railway and is named after its designer.

It was based mainly in London working express trains to the North East of England and Scotland.

In 1959 it set the official post war speed record for steam of 112mph and the locomotive finished its British Railways career in Scotland, having run around 1,500,000 miles.

In 1966 the locomotive was purchased by the A4 Locomotive Society, which later became a registered charity as The Sir Nigel Gresley Locomotive Preservation Trust, which still owns the locomotive.

It is now based at the North Yorkshire Moors Railway but also continues to run on the UK main line network, hauling rail tours to locations such as Chester, York, Carlisle, Bristol, and Dundee.