One of the "most important structures of medieval Scotland" has been rediscovered after being hidden beneath a Borders river for centuries.
Two years of work have led to the discovery of the "lost" medieval bridge in the River Teviot near Ancrum.
Experts, using radiocarbon dating, have confirmed it is from the mid-1300s.
They said that makes them the oldest scientifically-dated bridge remains found in their original position across one of Scotland's rivers.
Historic Environment Scotland (HES) has funded the Ancrum and District Heritage Society's (ADHS) work - in partnership with Dendrochronicle and Wessex Archaeology - which led to the discovery.
Built during the reigns of David II of Scotland and Edward III of England, the bridge is said to be of "historic and strategic national importance".
It crossed the River Teviot, carrying the Via Regia (The King's Way), on its way from Edinburgh to Jedburgh and the border.
It is believed James V would have crossed at the spot in 1526, as would Mary Queen of Scots returning from her tour of the Borders in 1566, and the Marquis of Montrose on his way to battle at Philiphaugh in 1645.
Kevin Grant, archaeology manager at HES, said it was one of the "most exciting and significant archaeological discoveries in Scotland in recent years".
"This project shows that discoveries of immense importance remain to be found by local heritage groups," he said.
He said it also showed what could be achieved by bringing "archaeological science and expertise together with local knowledge".
Geoff Parkhouse, from ADHS, said: "Ancrum Old Bridge now has a 14th Century date.
"In Scotland, there is not a standing bridge that is earlier than the 15th Century.
"In those times, during flood or highwater, the Ancrum Bridge may have been the only place to cross the Teviot between Hawick and Berwick, making it one of the most important structures in medieval Scotland."
Dr Coralie Mills, of Dendrochronicle, a consultancy specialising in tree-ring dating, said the structure showed the "rare survival of part of an early bridge in a hugely strategic historical location".
"The oak timbers are in remarkably good condition and provide really important local material for tree-ring analysis in a region where few medieval buildings survived the ravages of war," she said.
Dr Bob MacKintosh of Wessex Archaeology said the site had been "challenging to survey".
However, he said the results were "really exciting" with the bridge foundations being built using a method never previously found in an archaeological context in Scotland.
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