Archaeologist Daniel Sausins was expecting to find a few bits of equipment that had gone overboard from Chippenham Sea Cadets HQ when he went on a dive in the River Avon.

But instead he came up with a 2ft 6ins long sword that probably dates from the 18th century.

Mr Sausins, 23, of Winchester Close, Chippenham, said: "It was a real surprise. I went in looking for stuff the Sea Cadets might have lost and ended up pulling out a sword."

Mr Sausins, who studied archaeology at Bournemouth University and now works for an Oxfordshire company that carries out digs and excavations, said the sword is a long way from being one of the oldest pieces he has found but the circumstance was one of the more unusual.

Both he and his father Martin are members of Chippenham Diving Club. His father, who works for Westinghouse, said: "I am Chief Petty Officer of the Chippenham Sea Cadets and we were diving close to the HQ.

"Suddenly Daniel came up with this sword. It looked as if it had been in the water for a long time as it was all covered in barnacles and the handle had gone."

Pictures have now been sent to museums to get it properly dated. Daniel has had an avid interest in collecting and researching ancient artefacts since he was a boy. His father said: "It probably started when we went on family holidays to Greece and Turkey and there were a lot of ancient sites."

But one of the oldest pieces Daniel has found was much closer to home.

He said: "I was walking with my girlfriend just outside Chippenham and I saw a mesolithic core which dates from 6,000 BC."

He explained this was the left over shell of a piece of flint that had been used to create an arrowhead.

"It was a very unusual shape so I spotted it straight away."