The sword was excavated at Bamburgh Castle in 1960

Experts at the Royal Armouries in Leeds, say X-rays of the 7th Century sword prove it was made from a unique method using slices of carbonised iron.

The sword lay in a suitcase, after being unearthed in an excavation at Bamburgh Castle in 1960.

Archaeologist Paul Gething said the extremely rare sword would have had "serious bling factor".

After being "rediscovered" in a house clearance, the weapon was sent for a series of hi-tech tests.

They revealed the blade of the sword, which predates the Vikings, was made up of six, individual strands of carbonised iron bonded together.

Mr Gething, director of the Bamburgh Research Project, said: "This is an exceptional sword and a stunning find.

'Vastly superior'

"What makes it unique is that the billet is made up of six strands of carbonised iron, which have been micro-welded to bond them together.

"There have been swords found before which have been made of up to four strands, but none have ever been found with six.

"This is a vastly superior sword which, in its time, would have had serious bling factor."

Dr David Starley, Science Officer at the Royal Armouries in Leeds, added: "We see a lot of swords here, but have never seen anything like this before."

Bamburgh was the capital of the Anglo-Saxon kingdom of Northumbria, which extended from the English Midlands to Strathclyde.

It is thought the sword may have been bestowed as an ostentatious gift upon a king's highest ranking warrior.