A Viking helmet unearthed in Yarm in the 1950s is the first to ever be found in Britain, according to new research.
Found in Chapel Yard by workmen digging trenches for new sewerage pipes, the corroded, damaged artefact is a rare, 10th century Anglo-Scandinavian helmet.
A research project led by Dr Chris Caple also found it is only the second near-complete Viking helmet found in the world.
It has been on display at Preston Park Museum since 2012.
The age of the helmet had caused much debate until now.
Researchers used evidence from recent archaeological discoveries as well as analysis of the metal and corrosion to reveal its past.
Dr Caple, Emeritus Reader at Durham University, said: "It was a challenging project, as the thin iron sheet is now very susceptible to corrosion (it has to be kept in very dry conditions), so it was not simply a question of only showing the date at which it was created, but working out how it had survived until it was unearthed in the 1950s.
"Our analysis showed that it was initially preserved in waterlogged conditions, only later becoming damaged and starting to corrode. Fortunately it was discovered before it corroded away completely.
"Although there are half a dozen early medieval helmets from Britain, the Sutton Hoo and Coppergate helmets being the most famous, this is the first Anglo-Scandinavian (Viking) helmet from Britain.
"The only other near-complete Viking helmet is from Gjermundbu in Norway."
The Yarm Helmet remains on display at Preston Park Museum in Stockton.