The largest-ever post-war salvage operation on the Thames has discovered seven shipwrecks up to 350 years old.

They include a warship that was blown up in 1665, a yacht converted to a Second World War gunboat, and a mystery wreck in which divers found a personalised gin bottle.

The vessels, in the Thames Estuary, are just some of about 1,100 ships which went down in the whole of the river.

The salvage by Wessex Archaeology and the Port of London Authority, which regulates the river, was both historical and practical. Jagged metal from the wrecks which stick out of the mud, silt, and gravel act as a "can-opener" that can split apart vessels, especially large container ships which can skim within half a metre of the riverbed.

The operation was filmed for the BBC and took four months, using a dozen divers who used 3D survey equipment to locate the wrecks in near-zero visibility.

Frank Pope, the marine archaeologist who led the research, said: "This is the first time it's been done on this scale on the Thames, clearing to such depths - down to 16 metres - to get at ships this big." The ships explored by diving teams were:

• HMS London, the oldest wreck, found near Southend. It was collected by Charles II from Sweden during the Restoration. The 90-cannon warship was blown up accidentally in peacetime in 1665, just a year after its launch, killing 300 - but 24 people, including one woman, survived after being blown clear. Samuel Pepys wrote about the ship in his diary.

• An unnamed Tudor Thames brick barge found close to HMS London. Hundreds of yellow Kent bricks were found aboard.

• The Dovenby , a 70-metre, three-masted steel cargo ship carrying guano for fertiliser from Peru to Antwerp. It sank in 1914 after crashing into steamship Sindoro in fog, north of the Isle of Sheppey. The helmsman was killed.

• HMS Aisha, a yacht requisitioned to become part of "Dad's Navy" in the Second World War. It hit a mine north of the Isle of Sheppey in October 1940.

•A pottery carrier - one of seven that sank in the 19th century between the Dovenby and brick barge. Known as a Bawley boat, it was also used for shrimping.

• A mystery wreck labeled "5051", just south of Canvey Island. It went down in about 1862. A gin jug found on it is marked Mr White, owner of the Crown and Anchor, Woolwich.

• SS Letchworth, a collier sunk in November 1940 by the Luftwaffe en route from Blyth to London, sank of f Southend. All hands survived.

Finds from the various ships included cups, plates, well preserved leather shoes, bricks, the rare steel sailing mast of the Dovenby and a deck beam from the Aisha.

But any dreams of recovering chests of gold or well-preserved cannons were not realised. Some salvage operations had already been carried out after the ships went down. Divers using upturned bells to allow them to work underwater managed to save valuable bronze cannons from HMS London soon after it sank.

Richard Everitt, chief executive of the Port of London Authority, said: "This is the largest operation of its kind since submarine defences were removed at the end of the Second World War.

"We co-ordinated the whole process because we felt it was right we should get a long-term record of the history of Britain's second-largest port, and this very important part of the country's economy."

The first episode of two-part documentary Thames Shipwrecks: A Race Against Time is on BBC2 at 8pm tonight.

HMS LONDON

The wreck of the HMS London is so significant that the Port of London Authority is moving the shipping channel to avoid disturbing it. It has been dived on several times, and sections of wood have been recovered for archaeologists to analyse.

It sank with the loss of 300 lives when it was blown up accidentally after a sailor is thought to have taken a candle belowships. The vessel was in service when Samuel Pepys began to draw up his plans for Britain's navy. On 7 March 1665 Pepys recorded the event in his diary. "...This morning is bought to me to the office the sad news of the London, in which Sir J Lawson's men were all bringing her from Chatham to the Hope, and thence he was to go to sea in her - but a little a-this-side of the buoy of the Nower, she suddenly blew up.

"About 24 and a woman that were in the round house and coach saved; the rest, being 300, drowned - the ship breaking all into pieces - with 80 pieces of brass ordnance. She lies sunk, with her round house above water. Sir J Lawson hath a great loss in this, of so many good chosen men, and many relations among them."

HMS AISHA

The Aisha was purchased as a pleasure cruiser and lovingly renovated by one RH Turner.

She was, however, requisitioned shortly afterwards by the Navy and sprayed gunmetal grey inside and out, much to the dismay of Turner's wife.

As the Second World War broke out, the Aisha was crewed by civilians and retired seamen as part of the "Dad's Navy" Home Guard and helped to guard the Thames. She was part of the armada of "Little Ships" that evacuated Allied troops from Dunkirk in June 1... but was blown up later that year by a mine north of the Isle of Sheppey.

Following on from a geophysical survey earlier this year, there will be a full dive on the wreck to attempt to retrieve small objects before archaeologists decide whether to lift her fully or partially excavate her.

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