Archaeologists from Oxford Archaeology have uncovered the original eastern defensive line of the late Saxon town of Oxford at Oriel College.

The discovery confirms a hypothesis that had gone unresolved since the Victorian period, when excavations outside the Bodleian Library revealed a section of wall thought to be the original town’s north-eastern corner.

The whereabouts of the defences gives credibility to theories that the early fortified Oxford was significantly smaller than the later medieval town and had a square perimeter — built by the Anglo-Saxons according to the model of walled Roman towns such as Winchester.

Ben Ford, senior project manager at Oxford Archaeology, said: “The discovery at Oriel College is extremely exciting as it provides the first evidence since 1899 for the line of the original defensive circuit on the east side of Oxford.

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Oxford Archaeology team members extract cores of earth from deep beneath the surface (Image: Oriel College) “Using specialist equipment to extract cores of earth from deep below the existing ground level we have identified the profile of a large infilled ditch which is over three metres deep and about 20 metres wide running north to south.

“There is no sign of these defences now because over time the ditch had filled up with deposits and then been built over.

"Scientific dates from fragments of charred plants in the ditch show that it was probably constructed during the late-Saxon period, around 880 to 950 AD, which exactly aligns with the time Oxford is thought to have been founded.

“We hope that further study will obtain a more accurate date and solve this fundamental question about the origins of our modern city.”

Oxford City Council archaeologist David Radford added: “This really is a significant breakthrough that helps us get to the next level in terms of understanding Oxford’s emergence and evolution on the boundary between the kingdoms of Wessex and Mercia in the context of the Viking threat from the north in the 9th and 10th centuries.”

Colin Bailey, Oriel College’s master of works, said: “The ongoing project to rebuild the college’s kitchens and refurbish our bar provided a rare opportunity to excavate an area that has never been excavated before. It is fantastic to see this resolve a century-old debate.

“The city of Oxford has such an intriguing history. I find it extraordinary that, despite nearly 700 years of continuous existence at the same site, Oriel College continues to surprise us with new discoveries about the ground on which it is built.”

Oxford Archaeology is one of the largest independent archaeological and heritage practices in Europe, with more than 400 specialist staff working out of offices in Oxford, Lancaster and Cambridge.