SCIENTISTS from Southampton are among a team of archaeologists who have uncovered what could be one of the largest standing stones in the country.

The group, made up of experts from the universities of Southampton, Wales and Leicester, were working at the ancient Avebury stone circle when they made the discovery.

Top archaeologists from English Heritage and the National Trust say the stone could weigh about 100 tonnes, rivalling the largest megaliths at its fellow site in Wiltshire, Stonehenge.

The surprise discovery was made during work at the 4,500-year-old stone circle to straighten two stones known as the Cove, which have begun to lean over the last 300 years and which it was feared could collapse.

The team found the stone was buried much deeper beneath the ground than previously thought and that one of the stones, which stands 14ft above ground, continues a further seven feet below the surface.

Amanda Chadburn, inspector of ancient monuments at English Heritage, said: "We were amazed when we discovered that the stone went so much deeper than we expected.

"Ground-penetrating radar and probing had suggested it existed to only about one and a half to three feet below the surface.

"It is absolutely enormous and could weigh as much as the trilithon at Stonehenge."

It was planned to bring both stones at the Cove into an upright position but investigations show that only the other stone, which is 16ft high above ground and predicted to exist 1.25m below ground, needs straightening.

The monster stone will now be left in its current state as it is considered safe.

Rob Mimmack, property manager at Avebury for the National Trust, which owns the monument, said: "The stone is being fixed in the ground with lime concrete.

"Within two to three weeks we will be taking down the scaffolding and people will have access to the stones again for the first time since 1997, when they were fenced off for safety reasons."

The recovery of preserved organic material from soil samples during the excavations will enable radiocarbon dates to be taken.

For the first time the Cove will be able to be dated by modern methods.