Vince Goldup thought he had struck lucky when his metal detector bleeped and registered gold.

But when he dug into the mud on Minster beach his joy turned to horror as he unearthed a 200-year-old artillery shell.

He said: “I thought I’d struck gold and then out popped a bomb.”

Petty Officer Richard Ellis from the Royal Navy bomb disposal squad identified it as a pallisser round dating back to the 1800s.

His four-man team from Portsmouth retrieved it from the ooze then walked it into the sea where they blew it up with a controlled explosion.

Bemused sightseers along Minster Leas watched as the blast forced a huge plume of smoke, sea and sand into the air.

The drama began at noon on Monday when Vince, 34, who works in the Scope charity shop in Sheerness, was searching for treasure at low tide.

Since he bought his metal detector in June he has found two gold rings, one silver ring, a selection of costume jewellery and a stash of lead fishing weights.

He said: “Although I had been hoping to find another ring, at least it is nice to be able to have made the beach a little safer. The shell was only buried six inches below the surface.”

Coastguard officer James Crane said he believed the mortar-like shell had been shot from the former Army firing ranges at Barton’s Point.

A stretch of the beach was cordoned off with police tape until the bomb disposal squad arrived at 3pm yesterday.

Among those watching the exercise from the safety of a bench were pensioners Don Gray, 87, and David Blore, 85. The pair were taking a break from walking along The Leas.

Mr Gray, a retired ambulance driver, and Mr Blore, a former fireman with the London Fire Brigade, both live at Barker’s Court in Chalkwell Road, Sittingbourne.

Mr Gray said: “All the activity livened up the day. It was a nice surprise to get some free entertainment.”

Mr Crane warned: “If anyone finds anything like this on the beach they should leave it well alone, call 999 and ask for the coastguard.”