Twigs suggest Assynt site 'genuine Iron Age broch' Published duration 14 November 2011

image caption The remains of the broch at Clachtoll in Assynt

Radiocarbon dating of burnt twigs found inside an ancient building in Assynt suggest its interior remained untouched after it was built in the Iron Age.

Brochs were often modified during later periods of use. One at Nybster in Caithness has evidence of possible Pictish and medieval occupation.

The dating of twigs possibly used for woven mats points to the Assynt site remaining unaltered until it collapsed.

The broch at Clachtoll was built using stones weighing up to 100kg each.

Archaeologists involved in a community project called Life and Death in Assynt's Past had expected the burnt wood to date from AD 300 to AD 1000, during the building's final phase of occupation.

However, tests at AOC Archaeology's laboratory in Midlothian dated it to 111 BC and AD 55, suggesting generations of families left the interior unaltered from the time it was created.

A spokeswoman for the project said: "The possibility that we have a genuine Iron Age broch interior, untrammelled by later modification of admixture, is very exciting indeed."