SECRETIVE glimpses into Auckland Castle’s past have been unearthed by archaeologists.

Experts from Durham University are exploring the grounds before the site undergoes a multi-million pound transformation to become a major visitor attraction.

The Auckland Castle Trust, which now runs the castle, in Bishop Auckland, is keen to shed new light on 900 years of history and beyond.

The shattered remains of a building have been laid bare in a trench on an undulating grassed area close to the castle’s Scotland Wing - so-called because that is where prisoners’ from north of the border were once housed – alongside evidence of burning.

However, while the two finds sit together neither is historically linked.

The rubble, which includes finely worked stone, is up to 1.5m deep in places and lies over what is a substantial layer of burnt sediment and ash.

Auckland Castle’s head curator, Dr Chris Ferguson, said the vast volume of debris could suggest a “very dramatic end” to what looks to be a substantial structure or range of buildings.

Exact details are unknown, but Dr Ferguson believes it could be linked to the tumult surrounding the English Civil War or improvements undertaken in Georgian times.

“We knew there had been buildings in this area around the Scotland Wing, but didn’t know if anything remained,” he said. “We had hoped to find evidence of a tower but instead we have been left with something of a mystery, especially as we have no idea what the burning is associated with.”

However, there are no records of any particularly destructive fires or any other such traumatic events at Auckland Castle to account for the findings.

Natalie Swann, project archaeologist for archaeological services Durham University, said: “Under that burnt area there are substantial walls with a rubble core from a much earlier building and there is evidence of some nice facing.

“We’ve also found 18th century pottery but nothing earlier, but we are only scratching the surface at the moment.

“It’s all very interesting as whatever happened here is from a time when records were either vague or non-existent so anything we find will help add to the overall picture of the castle.”

There are 25 trenches in total around the Scotland Wing, in the walled garden and by the clock tower.

The dig is being funded as part of a wider Heritage Lottery Fund (HLF) supported project and is the first step in securing an additional £9m from the organisation.

It is hoped some of the finds from the archaeological dig, which include pottery from the 1700s as well as the medieval period, animal bones and stone carvings, will go on permanent display at the castle.