Archaeologists are searching for traces of the Roman army in Scotland in an attempt to solve a long-standing mystery.

Experts will begin the hunt for ancient artefacts at sites in Aberdeenshire, Angus and Perthshire next week.

The Romans built a number of outposts in northern Scotland, including the world's most northerly Roman fort at Stracathro, but their purpose is unclear.

Led by Andrew Tibbs, of Durham University, the archaeologists hope finding new military sites in the north east might help solve the mystery.

Mr Tibbs said: "We know that the Romans built a series of forts on the edge of the Highlands, and each fort at the entrance to the glens leads into the depths of the Highlands, but we don't know why.

"Was it to stop the Highlanders heading south and invading the Roman Empire or did the Romans plan to launch their own invasion of the Highlands from these forts?"

Any new discoveries made by the team are will probably be part of the Gask Frontier - a series of Roman forts and watchtowers stretching from Loch Lomond to Brechin.

Mr Tibbs added: "Any discoveries are likely to be followed up with further surveys and possibly excavation in 2018.

"There's so much we don't understand about the Romans in Scotland, including how far north they really went. We know they built a fort at Brechin and that there were Roman soldiers up in Elgin.

"If we can identify new military sites in the north east, we might be able to solve the mystery of why they built these forts on the edge of the Highlands."