A SCRAP of antler has proved that Silbury Hill, the largest man-made mound in Europe, is 4,500-years-old.

The first scientific evidence for the date of the ancient monument is one of two antlers found at the summit of the 128ft hill.

It was discovered as archaeologists agonised over how to fill a gaping hole which has threatened the collapse of the structure.

The fragments are the broken tips of the picks with which the hill was built, that were thrown into the top as the last gaps between the blocks of cut chalk were filled with rubble.

While the first phase of building at Silbury may be centuries older, the dating of the antler proves the structure was complete almost 1,000 years before the last arrangement of the boulders at Stonehenge.

The dating, by the Oxford University's Radiocarbon Unit, reveals a late Neolithic date of about 2490-2340 BC, with 95 per cent certainty of accuracy. Earlier attempts to date Silbury Hill were based on educated guesses of 2800-2000 BC its form is so unusual there is almost nothing to compare it with.

Amanda Chadburn, English Heritage's ancient monuments inspector for the area, said it was a significant find.

"These are the first antler picks that we have been able to date," she said. "It is a very exciting find which is producing high accuracy scientific results that we haven't had before."

Roman coins and the scraps of a medieval horse harness were found in the excavation.

The hill's construction was estimated to have taken more than three million working hours.

Meanwhile, the hole in the mound has been closed with blocks of polystyrene and a layer of chalk, and a seismic study, due within weeks, will show if Silbury is still unstable and in danger.

The collapse of the top of Silbury Hill last year is nothing new according to historian Brian Edwards.

His research has found the top had caved in on at least two previous occasions.

The first collapse in the 1930s is well documented, but Mr Edwards from Devizes has discovered there was another collapse a century ago.

www.english-heritage.org.uk