BBC East's Peter Laverock reporting on the operation to save Seahenge

The 55 posts, together with the up-turned stump of an oak tree in the middle, were first spotted on the beach at Holme, near Hunstanton, last November. They had become exposed after the peat dune covering them was swept away by winter storms.

Norfolk County Council's Archaeological Unit identified the find as a Bronze Age timber circle dating from around 2000 BC - roughly contemporary with Stonehenge. Inevitably, the circle was dubbed Seahenge.

Left to rot

It is thought timber circles were used by prehistoric cultures to expose their dead to the elements, birds and wild animals - a practice called excarnation. The belief was that allowing the flesh to rot from the bones in the open air would liberate the dead person's spirit.

How Seahenge could have looked 4,000 years ago

The archaeologists say the find is unique in Britain, and the best preserved example in Europe.

"This is the first time we've ever found a timber circle intact in Britain," said Mark Brennand of the Norfolk Archaeological Unit.

"The sites of timber circles are not uncommon, but up to now all we have seen are the soil markings where the timbers once stood before they crumbled away.

"Here, the circle was built in water-logged ground so it's never dried out and the timbers have been preserved,"

An upside-down world

What really excited the archaeologists was the discovery of the large inverted oak stump in the centre of the circle.

It is thought to have formed a sort of altar on which the bodies would have been placed to decay.

Archaeologist Maisie Taylor describes the conservation process

"Other circle sites we have looked at had large pits in the centre but we had no idea what caused them because the stump itself had long disappeared," said Mark Brennand. "Now we know what was there, we can go back and re-evaluate the sites."

Dr Francis Pryor, President of the Council for British Archaeology, believes the symbolism of the upside-down oak tree is very important to understanding the Bronze Age mind.

"We often find everyday objects deliberately turned upside down at Bronze Age sites. The inverted oak is a very complex statement. It is the world turned upside down, just as death is an inversion of life.

"From a ritual point of view it symbolises taking objects out of this world and placing them in the next. We're not absolutely sure what these people thought that next world was, but we think they envisaged a parallel world inhabited by their ancestors," Dr Pryor said.

Edge of the unknown

Forty centuries ago Seahenge would have been further inland, rather than on the beach as it is now.

An excavation by the Norfolk Archaeology Unit suggests that the circle was originally constructed on swampy ground up to a kilometre from the sea, which the waves covered at a later date.

Survey shows circle was built in freshwater swamp

Dr Pryor believes the positioning of the timber circle is significant. He suggests that to Bronze Age man the obvious symbolism of the coastline as a divider between two worlds, land and sea, made it an appropriate place to mark the transition between this world and the next.

Other archaeologists disagree. They think the position of Bronze Age funerary sites was chosen simply to mark the borders of land held by the family or community.

Studies of the Seahenge timbers could help answer another historical puzzle. Excavations of Bronze Age burial sites have turned up a disproportionate number of male remains. This might be explained if the bodies of many women and children had been disposed of in timber circles like Seahenge and the body parts scattered.

Uncertain future

The archaeologists have to work fast to save Seahenge.

The circle is close to the low tide mark on the beach and could be destroyed by wave erosion now it has been exposed.

English Heritage, the UK Government agency responsible for ancient monuments, is also worried about the numbers of sightseers and souvenir hunters visiting the site.

Specialists clean away the mud of forty centuries

To protect the fragile remains it was decided to remove the timbers and take them away for analysis and conservation. Once lifted, they would be transferred to Flag Fen, near Peterborough, an archaeological centre which specialises in the study of prehistoric timber.

But just a few timbers had been excavated when the archaeologists hit a snag.

Not everyone wanted the circle moved.

Protestors, including self-styled druids and some local residents, launched a publicity campaign to obstruct the archaeologists' plans, arguing that much of the importance of the circle lay in its location, and that it should not be moved.

The archaeologists have succeeded in getting a High Court injunction preventing some of the protestors approaching the site. The excavation work has been resumed and the transfer of the timbers to Flag Fen is expected to take two weeks.

Cleaned and preserved

Techniques similar to those used on Henry VIII's warship the Mary Rose will preserve the finger posts and the central, up-turned tree stump 'altar'.

Waterlogged timbers are perfectly preserved

The posts will be submerged in water tanks to protect them from deterioration. Subsequent forensic work will then include a general examination of the timbers, a study of tool marks, dating of the wood and examination of the activities of prehistoric insects.

Clear tool marks could provide important information on early Bronze Age wood working and construction methods. It is the first time that well preserved tool marks from a complete early Bronze Age site will be studied in Britain.