Rabbits are undermining the foundations of a Northumberland hill fort which has stood unscathed since Roman times.

The defences at Harehaugh survived the Roman invasion and 2,000 years of wear and tear.

But now the site is resembling a Swiss cheese after a rabbit colony made its home in the loosely-packed earth.

Scientists from Newcastle University have been called in to see what damage has been done by the burrowing.

Test trenches have been cut by experts

John Dore, of Newcastle University, said: "It would be nice if we could find some ecologically-friendly way of dealing with the rabbits and preserving the site.

"There is no doubt they are damaging the site."

He said ferrets had been used to try and remove the rabbits, but without success.

The alarm was first raised in the mid-1990s and a control programme started, but that has failed to curb the rabbits.

The scientists are cutting trial trenches at the fort to gauge the level of the burrowing.

They believe the Harehaugh site is a key historic hill fort in Northumberland.

The fort has multiple ramparts on its western side, thought to have been constructed to impress bands of raiders.

Hill forts were made up of large groups of houses, clustered together for protection on the top of hills.