Archaeologists are in a race against time to excavate a 4,000-year-old burial ground discovered just 20ft from a crumbling cliff edge.

The Bronze Age barrow was unearthed at Peacehaven Heights, east of Brighton, where cliffs are eroding at the rate of 2ft a year.

The mound is inching ever closer to the edge and will begin falling 200ft into the sea within ten years.

Project leader Susan Birks said: "We are trying to uncover the barrow's secrets before it goes to a watery grave.

"This is a rare opportunity to excavate a possible Bronze Age round barrow situated on a dramatic cliff edge before it and all its secrets are lost to the sea.

"The pace of coastal erosion means it is likely that the site will be unsafe to access within ten years and it probably will disappear altogether within the next 20 to 50 years."

English Heritage and the landowner gave their approval for volunteers from Brighton and Hove Archaeological Society and the Mid Sussex Field Archaeological Team to dig in the hope of discovering when exactly the grave was built, by who and for whom.

Ms Birks said: "Preliminary excavations were carried out in September, revealing clues to its construction and history.

Winter weather means we will have to return in the spring to continue.

"This is a rare opportunity to get an insight into a funerary monument built by our ancestors probably some 4,000 years ago.

"Most barrows are either totally ploughed out so that little evidence remains."

The volunteer archaeologists are not the first to dig into the barrow. Fragments of clay pipes found in the recent dig suggest Victorian grave robbers were the first to search the site.

The latest excavations also indicate the barrow was dug into during the Second World War by soldiers.

Ms Birks added: "We have uncovered two slit trenches that were dug in the barrow.

These were probably used by soldiers to defend the coast against enemy attack.

"Unfortunately, the soldiers or the Victorians may have destroyed evidence of a grave.

"Alternatively, we may yet find it intact."

Anyone interested in joining future excavations should contact Susan Birks at susan.