When Charles Trollope, an internationally renowned expert on historic ordnance, arrived at the Royal Armouries at Fort Nelson, Hampshire, to view five cannon salvaged from the sea, he came to a stark conclusion.

An historic site had apparently been stripped of valuable artefacts by an independent diving team and an important piece of Britain’s heritage was soon to be put up for sale.

So began a fight to save one of the bronze cannon, whose provenance is still in dispute, and to protect the remains of HMS London, a 17th-century warship, from the expeditions of profiteering salvage companies.

After an investigation by The Times and outrage among historians and marine archaeologists, English Heritage said that it had applied to have the wreck listed as a protected site, ensuring that further independent salvage expeditions were illegal.

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Mark Dunkley, a maritime archaeologist at English Heritage, said that there were several cases “where salvage and recovery of material from the seabed has been undertaken prior to archaeological investigation”. He said that the application to make the wreck a protected site had been made relatively recently but its whereabouts had been known for centuries.

Built at Chatham in 1655, HMS London was part of the fleet that escorted Charles II home from exile in the Netherlands after the Restoration.

A glorious career as the flagship of the maverick admiral Sir John Lawson was cut short on March 8, 1665, when she blew up in the Thames estuary. The accident may have been caused as sailors reloaded old cartridge papers with gunpowder. Men descended in a diving bell in 1665 to retrieve 18 of the cannon. Peter Le Fevre, an historian of the Restoration Navy, told The Times: “Another four came up in 1682 and another couple in the 1690s.”

In 1985 Mr Trollope was engaged in recording the precise origin of some 14,000 British cannon. He suggested to a Royal Navy curator that the bronze guns of HMS London ought to be retrieved. “Very few bronze guns survive,” he said. “They mostly went into the melting pot.”

Peter Steen, marine services manager at the Port of London Authority, said: “In June last year some person or persons unknown to me went out and removed some cannon from the wreck we know as the London. They subsequently reported the finds to the Receiver of Wreck, following the correct procedure.”

The Receiver of Wreck was notified in October last year of five cannon. Two were English, said to have been raised from the site of HMS London. Three were Dutch, reported to have come from outside English territorial waters.

Mr Trollope concluded that one of the Dutch cannon may have come from the site of the HMS London. “Like the English guns, it has no concretions on it, which would suggest it came from the same place,” he said. The surface corrosion was similar. Made in 1600, it may have been captured in the first Dutch War and refitted aboard the London, he believes.

Nigel Morris, of Sea-Lift Diving, confirmed that his company had been contracted to dive the site of HMS London by Vince Woolgrove, a certified dive supervisor. He said that he could not discuss where each of the five cannon was found. Mr Woolgrove has not responded to telephone calls from The Times.

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