A REPLICA Norman helmet discovered in a river by a family out swimming has experts baffled - despite exhaustive tests which narrowed down its age.

The antiquity recovered from the River Tyne was at first thought to be from the period of the Norman Conquest, but probably dates from the mid-19th Century.

Lindsay Allason-Jones, director of archaeological museums at Newcastle University, said: "At first sight, the helmet appeared to date from a period around the Norman Conquest.

"The nearest parallel we could find was the helmet in Prague Cathedral, traditionally thought to have belonged to St Wenceslaus, who died in 935AD.

"Similar helmets are also depicted on the Bayeaux Tapestry. If we could prove it was genuine, it had the potential to be one of the rarest, most exciting objects ever found on the British Isles."

However, aspects of the helmet suggested a more recent date, and it was sent to the Department of Scientific Research at the British Museum in London.

There, it was found to contain manganese, a metal only deliberately added to iron and steel to improve its qualities from the mid-19th Century.

Furthermore, a rivet fixing the nasal plate to the body of the helmet was found to be made of brass, a copper-zinc alloy, containing rather a high level of zinc for medieval brass.

Lindsay said: "Although we are now sure it isn't a genuine Norman helmet, there is still a mystery attached."

Museum staff think it could have been made for a pageant or amateur drama group and are determined to see the helmet dated more accurately.