For a century, the British warship HMS Hermes lay 30 metres down on the seabed, sunk by a torpedo and visited only by fish and curious divers who gazed through the gashed hull into the rotting ship's engine room.
For those who knew its history and location in the waters between the UK from France, the wreck was a shrine to the 44 people who died when a German U-boat attacked the cruiser during the First World War. For two modern-day British seafloor scavengers, it was an opportunity for plunder.
Within weeks of the centenary of the ship's sinking, the pair plotted to hook a line around a two-tonne lump of metal in the bowels of the engine room and winch it to the surface before selling it as scrap for £5,000.
The only problem: it wasn’t theirs. Nigel Ingram, an experienced but financially-strapped diver, and trawlerman John Blight were jailed for fraud on Friday after becoming the latest criminals to be convicted for the little-known but lucrative trade in underwater pillaging of wrecks.
In British coastal waters alone, an estimated 37,000 shipwrecks lie hidden, unmapped and – until now – largely untouched beneath the waves. The situation changed owing to a boom in global commodity prices that convinced organised crime and the greedy to systematically pillage metal components from the 20th-century warships, some of them war graves.
Officials are so worried about the underwater pillaging that they are using satellite surveillance over some of the most sensitive sites around Britain’s coastline.
While the costs of secret salvage are high, the potential for large profits make the risks and outlay worthwhile, according to experts. There is no shortage of material to find for the underwater asset-strippers.
“It’s absolutely stuffed down there,” said former policeman Mark Harrison who works for a heritage protection charity. “If they drained the Straits of Dover, it would look like a scrapyard.”
Experts believe that there are about a dozen salvage vessels, including Dutch and other European vessels, are involved in the systematic stripping of wrecks.
Despite being the world’s busiest waterway, hard-pressed authorities face an impossible task of policing beneath the waves of the English Channel. Only 53 of the thousands of wrecks have a special heritage status that means divers need licences to visit them.
“Vessels go to places where there are wrecks and turn their radar off,” said Simon May, an investigator for the Maritime and Coastguard Agency who brought the two men to justice. “Then suddenly they go missing for 10 minutes.”
Ingram, who was jailed for four years, and Blight, sentenced to three-and-a-half years, were caught only after tip-offs from British and French divers suspicious of what they were doing. About 100 items were seized from Ingram's home including bells, torpedo hatches and metal ingots which had not been declared to the authorities.
Their convictions mark the third time that Mr May has successfully prosecuted submarine metal thieves. In 2015, professional diver Vincent Woolsgrove was jailed for two years after raising three 17th-century cannons from a warship and sold them to a collector in Florida, who displayed them on his lawn.
The year before, two men were fined after scavenging artefacts on an “industrial scale” from nine wrecks over 13 years. They included cannon, pottery and ingots that were worth an estimated £250,000.
“To recover big items from the seabed, you need the infrastructure to do it and it starts to merge into organised crime,” said Mark Dunkley, a maritime expert for heritage organisation Historic England.
The authorities fear that the centenary of the First World War has encouraged treasure hunters to illicitly snatch items from ships. But the activities of Ingram and Blight were aimed at pure profit, according to British authorities, who recovered a notebook from Ingram’s home that detailed the dates, weights and prices of the metals they plundered.
The trophy that brought their downfall was the condenser, the ship engine's cooling system, that was prized for its copper.
Investigators said they believed the pair plundered metal worth some £180,000 between 2011 and 2012 from a ship still owned by the UK’s military authorities.
During 2011, copper briefly hit $10,000 a tonne, driven by strong demand from the US and China and disappointing levels of production from the major miners. It now stands at more than $7,000 a tonne, lessening the profit motive for such a costly crime to commit.
The underwater metal theft was a spillover from a surge in such robberies from land, including lead from church roofs and railway cables that cost the UK £1 billion in 2011. The problems prompted the government to set up a dedicated taskforce to crack down on the illegal practices in the scrap metal trade. Officials said its impact has been only limited in protecting historical wreck sites.
New technology and the shifting sea floor has led to the discovery of unknown wrecks off the British coastline, providing insight into the country's maritime past - but lured looters to the prospects of illicit profits.
The National joined a group of divers investigating the suspected theft of a bronze cannon from the sea floor off the holiday town of Southwold on the coast of eastern England after the gun had lain undisturbed for hundreds of years.
Local divers discovered the first of six guns from the site in 1994 after a fishing trawler dredged up a lump of timber from the seafloor embedded with about 50 cannonballs to reveal the presence of the wreck.
Little is known about the vessel which had long-since perished in the salty waters but experts dated the guns to about 1540. Enthusiasts lifted one of the guns, which was displayed at a local museum, but another was found to have gone missing in around 2015 – presumably looted.
The treacherous coast – the scene of a maritime battle in 1692 between British and Dutch navies - is littered with wrecks. A dedicated group of divers now carries out its own monitoring of the sites – despite the difficult conditions – to chart what is underneath the sea to protect it for the future.
“There are hundreds of wrecks around here,” said Andy Rose, a diver leading the team. “If you go through the books, it wasn’t unusual for several ships to be washed up on the shore during storms on the same night.”