The vastness of the discovery shocked researchers. It is believed to come from the Romano-British period – the 400 years the Romans ruled large parts of the UK. Virtually all of England and Wales came under their rule, as well as southern Scotland for a short period.
The fresh discovery of a dilapidated roundhouse was unearthed at Bamburgh Castle in Northumberland.
Foundations of the 40ft (12m) structure were discovered by volunteers from the Bamburgh Research Project.
It is believed to be more than 2,000 years old.
On looking at the foundations layout, excavators said they believe the original structure could date back to the Roman occupation of Britain.
Whoever lived at the coastal site before the Anglo-Saxon kings is unknown.
It is hoped that the newest find could hold “vital clues” about the transition from the Roman period to Anglo-Saxon England, Mr Young said.
Mr Young explained the discovery could give insight into a time before the Anglo-Saxons came to Britain.
He said: “While we have a good understanding about Anglo-Saxon life at the ruling capital of Bamburgh, there are many theories surrounding the Roman period up to the life of the early medieval kings.
“Everyone expects continuity, and this discovery has the potential to give us fascinating evidence and flesh on the very bare skeleton about the continual occupation of Bamburgh.”
The Armstrong family, who privately own the castle, are funding further archaeological investigations at the roundhouse site in the coming weeks.