A group of about 12 druids and environmental campaigners sat on the centre of the historic structure, known as "Seahenge, to prevent English Heritage from moving it.

The structure consisted of the upturned foot of an oak tree surrounded by an oval of 55 oak trunks.

It was uncovered last November by a local nature warden when the peat dune covering it was swept away.

Museum plans

Experts say the structure would have been erected at about the same time as Stonehenge and is one of the most exciting prehistoric finds which have been made.

They say there is a serious risk of Seahenge being destroyed forever by coastal erosion if is is not moved. English Heritage decided it should be uprooted and moved to an archaeological centre near Peterborough.

The central foot of an oak tree is surrounded by 55 oak trunks

It plans to take it to the Flag Fen Archaeological Centre near Peterborough where it will be stored in special water containers and analysed.

In the long-term it is planned to put the circle in a museum in the west or north Norfolk area.

But there has been great opposition from local people and environmental campaigners, who say the sea has cared for it for 4,000 years and should be allowed to carry on doing so.

The protesters sat on the central oak stump at low tide on Tuesday to prevent it from being removed by two mechanical diggers and the operation was called off for safety reasons.

'Site destroyed'

They were led by Buster Nolan, 50, a veteran tree campaigner from Great Bardfield, Essex.

He said he was delighted that the protest had worked, but feared English Heritage staff would return and move the tree base when protesters had gone.

"The message people must take is that if you find a sacred site in England hide it, bury it in the sand," he said.

"Don't tell English Heritage you have found an ancient site. They will steal it from you and put it in a museum where only the rich can see it.

"The site has already been destroyed as far as we are concerned because English Heritage have removed many of the oak posts and have bored into the central section with a chainsaw.

"But we can put the oak posts back if necessary, if the tree bole is taken away then it will be lost forever."

The protesters were backed by Geoff Needham, Chairman of Holme Parish Council and an expert on local tides and sea conditions.

He said the overwhelming majority of locals wanted the circle to be left where it was, as it was and not touched.

Learning from history

"It belongs here, it is part of England's heritage, it is part of Norfolk's heritage and it is part of our village's heritage.

"It will not get washed away. It is embedded in clay."

David Miles, English Heritage's Chief Archaeologist, said he sympathised with the protesters and was in favour of preserving historic sites whenever possible.

But he said in this case there was a severe danger of the circle being eroded away and lost forever if it was not moved.

"It's not just a question of moving it for the sake of it. If we move it we can preserve it and study it and learn all sorts of things about it that we'll never be able to know if it is washed away," he said.

He said English Heritage would now try to arrange another day when tidal conditions were suitable, for the central part of the circle to be lifted away.