Archaeologists in Monmouth have discovered the remains of an ancient wooden building that dates back 5,000 years.

The wooden remains found under the new Rockfield estate were once part of a crannog, an ancient fortified dwelling built into a lake, and they date back to around the year 3,000BC.

Monmouth archaeologist Stephen Clarke is the author of 'The Lost Lake,' which describes the discovery of a huge post-glacial lake which covered most of this area 10,000 years ago. Mr Clarke has revealed that this latest discovery predates the only other known crannog in England and Wales by 2,000 years.

The timber, which was skilfully worked with a stone axe, was unearthed during the digging of house foundations at Jordan Way by Martin Tuck of the Glamorgan-Gwent Archaeological Trust in 2003 while the group were overseeing the construction of the new Rockfield Estate.

The timber was preserved beneath the clay and peat of a lagoon which formed when the lake drained some 2,000 years ago and was recently given to Monmouth Archaeological Society whose professional wing – Monmouth Archaeology – is to watch over the construction of 450 new houses for Barratt Homes along Wonastow Road. That development is all on the site of the prehistoric lake.

The timber has been dated back to the New Stone Age (the Neolithic) before the invention of metalworking.

At this time, the Rockfield Estate, like most of Monmouth, was under a post-glacial lake which had formed at the end of the Ice Age, some 11,000 years ago.

The lake is thought to have survived until the 1st Millennium BC, probably not long before the Romans arrived; it has been partly explored by Monmouth archaeologists over several years at the Parc Glyndwr housing estate off Rockfield Road and earlier in upper Monnow Street and St James' Street.

The Stone Age timber, bearing cut marks left by stone or flint axes, formed the end of an oak post which had been carefully levelled to create a flat surface which would probably have rested on a post pad set in the bottom of the lake.

Archaeologists are excited, not only by the state and date of the timber, but also because the remains were so far out from the shore of the lake that the post has to be part of a crannog building set on poles.

Crannogs are defended wooden structures usually found in Ireland and Scotland and date from the Stone Age onwards – the only one known in England and Wales is that at Llangors, near Brecon. They are thought to have been a mark of power and status. The one at Llangors being claimed as a royal residence of the Dark Age King of Brycheiniog.