MONMOUTH archaeologists have discovered what is believed to be one of the most important prehistoric finds.

What was at first thought to be a longhouse is now believed to be an ancient boatyard.

Archaeologists have been working at the Parc Glyndwr building site, between Rockfield Road and Watery Lane, Monmouth, for about two years.

They first uncovered the remains of a huge post-glacial lake which survived in the bowl of Monmouth almost into Roman times and was overlooked by human settlements for thousands of years.

In his new book, The Lost Lake, Steve Clarke, chairman and founding member of Monmouth Archaeological Society, tells the story of the lake –which measured 4km across and six metres deep and ran around the higher ground of Monmouth to Croft-y-Bwla – and of the boatyard.

“It is the most important pre-historic discovery we have ever made. As far as we, know no-one in Western Europe has ever recovered a prehistoric boatyard,” said Mr Clarke.

People lived by the lake from at least 6000 BC, through to 100 BC. The lake broke through the bowl and drained in the 1st century BC: it left a lagoon which silted up and filled with peat.

When three channels cut across a Bronze Age burnt mound (dated 1680BC) were unearthed on the edge of the lake, they were at first thought to be remains of a structure such as a longhouse, until further excavation showed they were a hundred feet long, perfectly parallel and level and contained evidence of wood working.

Mr Clarke said: “The features were recognised as the ‘matrix’ for the construction and launching of a double canoe with an outrigger, as depicted in Bronze Age rock carvings.”

The Lost Lake is published by Monmouth Archaeological Society. £15 from Monmouth Museum, or Clarke Printing, Town Wall, Monmouth.