Contractors have completed the temporary works, including a giant cofferdam the size of two football pitches, and building of the new £38 million facility will now begin in earnest.

North-West Norfolk MP Henry Bellingham was invited to tour the site on Friday (22) and perform an official ribbon cutting to mark the new phase of the development.

Once completed, the new pumping station on the Middle Level Drain will protect around 70,000 hectares of land, 25,000 homes and 1,000 businesses from flooding and is set to be the largest of its kind in Britain.

The next stage of construction will see the cofferdam, built to protect the site, pumped dry and more than 400, 50-foot long piles inserted within it to anchor the foundations of the site.

Chief executive of the Middle Level Commissioners Mr Iain Smith told the Lynn News work was now on schedule and the new station was expected to be completed by autumn next year.

The overall project, including the demolition of the old pumping station, built in 1934, is due for completion in January 2010.

Speaking before leading a tour of the site, chief engineer David Thomas told visitors the new station was "a once in a lifetime project."

"We are here to mark a very significant stage, we're moving from temporary works to actually constructing the new station, though the temporary works themselves are a significant engineering feat," he added.

Mr Thomas said once completed, the six-pump station, which is being paid for by DEFRA, the Environment Agency and the rate payer, would be able to pump 100 tonnes of water a second and would protect Middle Level farmland valued at around £3.6 billion.

Cutting the ribbon, Mr Bellingham said "a big thank you" to contractors Atkins, Birse, KSB and Costain for the consideration they had shown the local community.

He added: "At a time of climate change, it's never been more important that we invest in sea defences and tidal defences."

Mr John Sheppard, project manager for Atkins, said: "This is currently the largest cofferdam in the UK and it's an incredible piece of civil engineering.

"The new pumping station will be architecturally significant. In the past they have been rather functional, but we wanted to get architects on board because it's going to be there a long time."

The old pumping station was found to be structurally unsound and its 50-year-old pumps struggled to cope with the last major flood in 1998.

More information about the project can be found at www.mlcpumping.info