Sift through the mud on the shores of a Canadian river and you'd be lucky to find a lost necklace amid the washed-up bottle caps and beer cans. But take a walk along the edge of London's River Thames, and there's a good chance you'll find a piece of ancient history.

It's this chance to dig up the past that has lured so many history buffs to the shores of London's Thames at low tide, where they hunt for washed-up artifacts in a hobby called "mudlarking." These treasure hunters routinely pluck all manner of mind-blowing items out of the mud, from medieval coins, to 2,000-year-old Roman relics, to the remains of pre-historic rhinos and sharks.

New treasures are revealed on the banks of the Thames twice a day, when the river's tide goes out and the water level drops by seven metres. That's when mudlarks – all of whom must be licensed – climb down ladders to the freshly-revealed foreshore and start hunting for historical goodies.

Veteran mudlark Jason Sandy says every trip to the foreshore offers a new set of surprises. "You never know what you're going to find," he told by phone from London. Sandy explained that boats are constantly stirring up the waters of the Thames, churning items out of the silty riverbed. Sandy finds all kinds of items, from modern objects to relics from hundreds, even thousands of years ago.

"Everything is kind of laundered together," Sandy said. "You can have a modern cigarette butt next to a prehistoric flint tool… Every day is a new surprise."

Sandy first became involved in mudlarking in 2012, when he used to take his two young children down to the foreshore to hunt for crabs and shrimp at low tide. He got the idea to look around for treasure from a TV documentary, and soon, he was doing it as often as possible.

"I just couldn't believe that you could actually go down there and find these historic artifacts that are that old," he said.

Sandy has found all kinds of relics since 2012, including a few that are now part of museum collections. "That's every mudlark's dream, to have something that's on permanent display in a museum," he said.

One of Sandy's earliest finds, a 2,000-year-old carved bone hairpin from Roman times, is now part of the permanent collection at the Museum of London. Sandy has also donated a pin associated with the infamous King Richard III to a visitor's centre and museum in Leicester.


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"We find incredible artifacts which you can't even find on archaeological sites," Sandy said. "We find them in the Thames."

He says the museum is also interested in acquiring a merchant's token he found earlier this month, which dates back to the Great Fire of London in 1666. "The Fire of London started very near where I found the coin," he said. "To find something like that is the quintessential find that any mudlark is looking for, because that's a key date in London's history."


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Sandy and his fellow mudlarks have a close relationship with the Museum of London, where they are required by law to show all of their discoveries that might be older than 300 years. An agent at the museum records everything, offers some history on the finds, and occasionally requests the best pieces for the museum's collection.

The museum also keeps a tight leash on mudlarking activities around the Thames, to ensure that the landscape is not torn apart by treasure-hunters. The southern shore is open to anyone with a mudlark's licence from the government, but individuals are not allowed to dig more than a few centimetres down into the mud.

Restrictions are even tighter along the north shore, where the ancient Romans first founded London, and where some of the oldest artifacts remain. A select group of about 50 mudlarks are allowed to search along this shore, and to dig up to a metre deep in search of treasure.

For standard permit holders, metal detectors are allowed on the south bank, but not on the north one. However, Sandy says he finds plenty of treasures while searching by eye on the north bank.

Sandy says the absolute best time to mudlark is at midnight in the summer, when the tide is as low as it gets. When this happens, a few brave mudlarks head to the foreshore to pore over the areas they normally can't access. "We put on our head torches, and we literally crawl around on the foreshore in the middle of the night looking for lost artifacts that are of historical value," Sandy said. "It's quite insane."

But, while Sandy and his ilk have unearthed many historic treasures from the edge of the river, a few mysteries remain.

One is the vast quantities of tiny garnets often found on the foreshore. Sandy says no one is certain where these red, semi-precious gemstones come from, but it's a popular topic of speculation among the mudlarking community. "It's quite strange," he said. "Some are gem quality, others are quite rough."


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Some suggest the gems might have been used for sandblasting in the past. Others think they might have fallen out of a shipment to a jeweller's shop along the river.

If the answers are still in the Thames, Sandy says he's determined to keep looking for them. "Every day is a new surprise that comes up from the Thames," he said.

"You never know what you're going to find."