With its thruster motors fighting the current, the submersible pushed through a blizzard of sediment. Far above, in a darkened control room, the robot's operator squeezed his eyes shut to push away the fatigue. Making three dives a day, he had lost count of how many times he had approached suspected wrecks only to find a clump of ferrous rocks or junk from a ship. This time it would be different.

The announcement this week that Odyssey Marine Exploration, the world's biggest commercial shipwreck exploration specialist, has discovered what appear to be the remains of HMS Victory has caused a sensation. At the time of her sinking in 1744, the Victory was the most powerful warship in the world and was the immediate predecessor of Nelson's flagship now berthed at Portsmouth.

The 240ft Odyssey Alert had towed high-frequency sonar and sophisticated metal detectors across the search area, identifying anything that did not appear to be natural. Odyssey Marine had surveyed about 4,700 sq miles (12,170 sq km) of ocean floor in the Western Approaches of the English Channel alone. Then the 251ft Odyssey Explorer arrived with the robot Zeus to take a closer look with cameras.

About 270 wrecks had been found so far, but on paper this latest target did not appear to be important. Then, into the glare of Zeus's halogen lamps, loomed a huge bronze cannon. “It was pretty amazing,” said Greg Stemm, Odyssey's chief executive. “We knew the Victory was out there somewhere, but we were expecting this 110-gun ship to look huge — but it was a tiny reading. We almost missed it.”

The robot continued its exploration of the site, hovering just above the shifting sands, camera strobes flashing every few seconds as the wreckage passed beneath. A thin veil of marine life shrouded the pulley wheels, bricks and a copper cauldron from the galley. Octopuses shrank into cracks; crabs scuttled from the lights. Then the high-definition lens came upon the first of the enormous bronze guns. Iron reacts with seawater to form bulging, misshapen concretions, but bronze survives well. The proud crest of the 42-pounder — the biggest cannon to be made by the Royal Navy — stood out, crisp and solid against the swirling water.

Long splinters of wood lay exposed on the surface. Then the remains of the ship's 35ft rudder appeared. The fibres of what was once the heartiest oak on the ship had almost disappeared, leaving little but the iron hinges. Organic materials survive centuries of immersion only if sealed off from oxygen, but the Channel's sandbanks shift continuously. The first time that Zeus enabled a count, there were 31 cannon. The next time, 41.

Adding to the confusion is the damage caused by Man. Not the bottles, nets, and knots of plastic that littered the site, but trawlers. Many of the cannon appeared to have been dragged out of their original alignment, and some bear what appeared to be gouges on their surface.

The wooden remains hold the key to how the great warship sank. For 265 years Victory was thought to have struck low- lying rocks off the Channel Islands during a storm, but her remains had now been found 60 miles away in open water. How did she meet her doom? The answer to another mystery lies somewhere on that patch of seabed.

Naval commanders and their crews were rewarded with prize money for capturing enemy ships. But Royal Navy vessels also acted as armed couriers for valuable private shipments, taking a 1 per cent cut. Merchants did not want to advertise how much was being transported, however. The Victory is the only first-rate English warship discovered under water and promises to reveal how much naval commanders could expect to profit.

The Victory was last seen afloat by the commander of the Duke, one of the 33 ships in Admiral Sir John Balchin's fleet, on October 3, south east of the Isles of Scilly. A storm was still building and the Victory was already struggling. Eventually the wind shredded every sail on the Duke and left ten feet of water in her holds. Another ship lost her main and mizzen masts but all survived the storm, except for Victory.

For all her might, Victory had been cursed by her prestige. Designed by committees of naval top brass, the ship took 11 years to construct in the Portsmouth yards — nearly three times longer than it had taken to build the similarly sized Royal George. The result was top heavy, and notoriously unseaworthy.

The builders had run into other problems. By the mid-18th century Britain was running out of shipbuilding timber, and it would take about 6,000 trees — 90 per cent of them slow-growing oak — to build Victory. To make matters worse, in the 1730s, as she was being built, an unnaturally warm summer caused high levels of sap in Britain's trees. Rather than seasoning, the felled wood rotted.

This clue is not lost on Sean Kingsley, an archaeologist working on the investigation. “In the final analysis,” he said, “it may very well have been the unfortunate use of rotten wood in HMS Victory, the mightiest warship in the world, that broke her back in the storm.”

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