A section of the mosaic, found at a Roman site near Boxford in Berkshire

A spectacular Roman mosaic described as the best find of its kind in half a century has been partly uncovered in Berkshire, during a community archaeology project that only had two weeks left to run.

Anthony Beeson, an expert on classical art and a member of the Association for the Study and Preservation of Roman Mosaics, described it as “without question the most exciting mosaic discovery made in Britain in the last fifty years”.

The newly discovered Roman mosaic

Luigi Thompson, an artist known for his meticulous paintings of mosaics, called the find, which dates from about AD380, “the most delightful, lively and charming pavement I have ever seen”.

Less than half the mosaic, a six-metre strip richly patterned with mythical characters, was uncovered in the last two weeks. It has now been buried again to protect it.

The central panels depict the Greek hero Bellerophon riding the winged horse Pegasus. They are shown attacking the fire-breathing monster Chimera, then being offered the king’s daughter as a reward, a legend that would later be Christianised as St George and the dragon.

Other scenes on the mosaic include imagery not known from any other British site, according to the experts.

The find was made at a Roman site near Boxford where residents and amateur archaeologists and historians, supervised by Cotswold Archaeology, have been excavating since 2011.

In the the last three summers, backed by the HeritageLottery Fund, they have found the remains of a large villa and bath house, a farm building, and now the mosaic.

The volunteer excavators, many with no previous experience, hope to raise funds to return next year.