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​Timbers believed to be from a unique 5,000-year-old logboat have been discovered on a building site in Wales.

​The prehistoric remains found at Monmouth have been radiocarbon-dated to 3,210 BC, in the New Stone Age.

“There are cut features which appear to make it a complex craft and one that may be unique in maritime archaeology,” said archaeologist Steve Clarke, the founder of Monmouth Archaeology.

Work on the 470-house development was suspended temporarily by David Wilson Homes to give the archaeologists enough time to investigate and record when deep drainage excavations uncovered the remains.

The site lies on the shore of what was once a huge lake caused by an Ice Age blockage in the Wye gorge and covers much of today’s town.

“As we had just discovered a rich Bronze Age settlement a few fields away we thought the remains would turn out to be Bronze Age,” said Mr Clarke, “so it was a real surprise when the dates came back as being twice as old.”

Two years ago, and less than 1500 metres away at Parc Glyndŵr estate, Monmouth Archaeology, a professional body that contracts to oversee building works, found boat-shaped channels in the clay at right angles to the lake with evidence of woodworking with flints which they interpreted as prehistoric boat-building, possibly a first such site in Europe.

On the same estate they identified remains of what appears to be only the second crannog - a building on stilts - in England and Wales - out in the lake, also New Stone Age and with a radiocarbon date of 2,917 BC.

The identification of the logboat is confirmed by criteria set out by a maritime archaeology expert in 1978 under which the remains have to meet at least two of six features: the Monmouth boat meets four of the six.

There are five timbers, all of oak, and all of which have been partially burned: two of them have worked features, two others could also be part of a boat while the fifth piece appears to be an unworked oak log.

The largest of the worked timbers is assumed to be the gunwale at the stern or bow of the logboat. It has an enigmatic oval-shaped open-ended hole, 4.8cm wide, and cut vertically into the surface of the wider end of the gunwale.

If this was to take a rope, it was broken where the pressure would have been greatest. There was also a deep ‘U’ shaped groove, possibly cut in the stern, which may have been to accommodate a central steering oar.

The second worked timber appears to be part of the hull of the boat. It has a large round hole, this time 7.5cm wide, cut through it horizontally where there are extensive signs of wear.

This feature may be to take an oar or be associated with the attachment of an outrigger or of the boat to a second one.

Mr Clarke said: “These latest discoveries make it vitally important that Cadw and Glamorgan-Gwent Archaeological Trust reverse their advice that there is no need for an archaeological watching brief ​on another proposed development site which is also on the bed of the lost lake and just yards from prolific Stone Age to Iron Age remains.

"We are appealing to our AM, Nick Ramsay, to ask the minister to intervene if necessary.”

However, he said members of the team were delighted with the help and cooperation they were receiving from David Wilson Homes and Barratt Homes during the development.

A revised edition of Steve Clarke’s book The Lost Lake, about the archaeology of the Monmouth Lake, has just been published and includes a supplement about the Monmouth Boat.

It is available from Monmouth Archaeological Society at £15 plus p&p, The Town Wall, Monmouth; mon.arch@btconnect.com.