University archaeologists make exciting and unexpected discovery at Chester Castle

Professor Stewart Ainsworth, Time Team’s Landscape Archaeologist and Visiting Professor at the University of Chester, ventured deep underground to investigate the remains of the 18th century prison beneath Chester Crown Court, where he stumbled across the stonework at the end of a dark, dingy, corridor.

He explained: “The walls of the prison and courts designed by Thomas Harrison are typical late 18th century masonry. It was dark at the end of that old corridor – but by the light of my phone I could immediately tell that a large section of wall in the gloom ahead was totally different. It turned a right angle and disappeared out of sight, leaving a very dark, narrow gap that I couldn’t squeeze into.

“When I compared the type of stones and the building technique with the surviving parts of the Norman castle, it was clear that this underground wall must also be medieval. Until now, everyone has believed that Thomas Harrison destroyed this part of the castle to create the buildings we see today.

“But the wall I discovered is massive – almost three metres high – so we now know that he left a lot of the medieval stonework untouched. And I’m guessing much more may survive under the car park and castle complex.”

High-resolution digital scanners were used to pinpoint the location of the underground wall. A comparison with old maps and plans showed it was once part of a medieval bridge across a deep ditch surrounding the castle’s strongly defended inner ward. The bridge was probably built about 800 years ago, in the 1260-1280s, when a heavily fortified gateway was added to the inner ward to replace an earlier gateway. Thomas Harrison subsequently demolished that 13th century gateway.

The castle’s original stone gateway, now known as the Agricola Tower, is looked after by English Heritage and is open to visitors at weekends. On the first floor of the tower, the chapel of St Mary de Castro contains fragments of rare and beautiful wall paintings dating to the 1240s.

The newly discovered wall at Chester Castle is very similar to part of the bridge across the deep ditch at Beeston Castle, the remains of which visitors can still see today. There, a drawbridge could be raised to prevent attackers reaching the twin-towered, 13th century gatehouse. It is likely that a similar arrangement once existed at Chester Castle.

The underground remains and other parts of the castle have been digitally scanned by the University and SCCS North to create highly accurate 3D models as part of Digital Dimensions, a collaborative project between the University, Cheshire Constabulary, English Heritage, Historic England and the Hartree National Centre for Digital Innovation. It is funded by the Arts and Humanities Research Council (AHRC), part of United Kingdom Research and Innovation (UKRI), and through the Heritage Science Data Service (HSDS), part of the Research Infrastructure for Conservation and Heritage Science (RICHeS) programme.

This project was led by the University’s Professor Ainsworth and Cheshire Constabulary’s PC Jonathan Lightfoot, along with the University team of Professor Meggen Gondek and Immersive Technologies Specialist Alex Foster, to test methods of digital recording and analysis to help prosecute and deter theft and damage of historic stonework. It is part of a national initiative in the fight against heritage and cultural property crime.

As part of the partnership, 72 police officers from forces across the North West and North Wales took part in a heritage crime day of training at Chester Castle earlier this year, giving an insight into how heritage professionals can support each other, with Professor Ainsworth delivering a session of graffiti and the theft of historic stone.

PC Lightfoot said: “I think it is amazing that by doing proactive surveys and recording of historic buildings, we are able to discover unknown archaeology. This just shows we can now safeguard this bit of history so we can learn from it for future generations.”