It was a chilly and dark morning as I exited the train station at Wapping in East London. Under the orange glare of streetlights, I changed my trainers for a pair of dirty wellies. People walking in the other direction, heading to work in business clothes, stared as I pulled on my plastic gloves. My office for the morning awaited so I turned down a narrow alleyway and carefully made my way down an uneven flight of steps, slick with green river weeds. Today I was going “mudlarking”.

If you find yourself crossing one of London’s busy bridges and look down, you may notice that the height of the Thames changes dramatically over the course of the day: the tidal river can rise and fall by as much as 7m. When the tide is out, you may see people scurrying down hidden stairs, ladders and slipways to trudge along the foreshore. These are “mudlarks” – and they play a vital role in preserving the history of the Thames by picking up objects and artefacts lodged in the river’s mud.

The Thames is especially rich in small portable finds; it’s not only their quantity but their quality that makes Thames finds so important

Walking along the foreshore of the Thames in central London is not everyone’s idea of a hobby – it can be cold, dirty and just as muddy as mudlarking suggests. Historically, being a mudlark was not a desirable station in life. The terms came about in the Georgian and Victorian periods when the Thames was one of the major routes to transport goods into the city. At this time, the banks of the river would have swarmed with the melancholy figures of mudlarks, mostly poor women and children who would be “up with the larks” to work whenever the river ran low.

As the tide dropped, they would wade into the mud to grab lumps of coal, pieces of rope or anything else careless boatmen had dropped overboard that they could sell. Mudlarks were a chiefly London phenomenon because few port cities had as large, exposed riverbanks where they could descend to do their work. In addition, the mud of the Thames is anaerobic – having very low levels of oxygen – so is perfect for preserving organic material that would otherwise rot.

Despite its humble origins, mudlarking is undergoing a renaissance. It has never been easier for people to explore the Thames: anyone looking for inspiration just has to follow the mudlarking hashtags on Twitter, Instagram or Facebook. The Thames Discovery Programme, a group of historians and volunteers, run guided tours of the foreshore where “expert guide[s] will point out fascinating archaeology hiding in plain sight like Saxon fish traps and jetties that once led to Tudor palaces… and [ensure] that you stay safe and stick to Port of London Authority rules,” said Josh Frost, senior community archaeologist with Thames Discovery.

While these tours are a great introduction to communal mudlarking, most mudlarks are solitary creatures and can often be found on their own, staring at the stones beneath their feet.

One of the surprise best-selling books of 2019 was Mudlarking: Lost and Found on the River Thames by Lara Maiklem, who stumbled into mudlarking almost by accident. “One day I found myself at the top of one of the river stairs looking down onto the foreshore and I decided to go down,” she wrote. “For some reason, until then, I’d thought of the foreshore as a forbidden space, sometimes revealed, other times covered over with water. I found my first object that day, a short piece of clay pipe stem, and I was hooked.”

My story was similar. Always tempted to play the archaeologist as a child, I dreamed of striking it rich by finding King John’s lost golden treasure that sank in a river. One day, long after I should have given up such fancies, I read about mudlarking online. I ran down to the Thames and pulled out my first treasure: a broken clay pipe last smoked by someone in the 18th Century. Now I can be found under London Bridge looking for Roman pottery; in Rotherhithe searching for industrial relics; and around Putney for prehistory. The joy of mudlarking is that you never know what might turn up or where.

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The Thames is one of the greatest and largest archaeological sites in the world, and the entire history of Britain can be told from items found on the foreshore. Many objects in the Museum of London have labels giving their provenance as “Discovered in the Thames”. Even a cursory glance at the river will reveal broken pottery pieces, shards of glass and twisted pieces of metal, and mudlarks have discovered everything from woolly mammoth teeth to Roman lamps to Tudor rings.

Given the lack of funding in archaeology in the past few years, the amateur eyes of mudlarks have been incredibly helpful in pointing out fragile structures emerging from the mud, with the Portable Antiquity Scheme (PAS) having just recorded its 1,500,000th archaeological discovery made by members of the British public.

“It is tremendously important that mudlarks report their finds to the Portable Antiquities Scheme in accordance with the terms of their licence, no matter how trivial or mundane they seem,” said Stuart Wyatt, Finds Liaison Officer for the London area, who assesses and records the artefacts found by mudlarks for the PAS.

“The Thames is especially rich in small portable finds; it’s not only their quantity but their quality that makes Thames finds so important. The preservation of lead, leather and bone artefacts is especially good, whether a Roman bone hair pin or a 17th-Century child’s pewter toy. These artefacts are often lost on land sites due to adverse soil environments, but the anaerobic qualities of the Thames foreshore preserve them.”

However, mudlarking can be a risky hobby. When the tide turns, it turns fast. You must always be aware of your route off of the foreshore. The mud is another hazard: on one of my first mudlarking trips, a more experienced mudlark told me how he had once fallen into a pit left in the mud. He was lucky to have a bucket to claw his way out – though the Tube ride home was a little dirty.

But it’s the mud of the Thames that makes mudlarking so rewarding. The layers of dirt contain artefacts from every stage of London’s history and pre-history. Liz Anderson, a mudlark who runs a blog about her finds, once pulled a 2,000-year-old Roman nit comb from the mud. “The comb is made of boxwood and what I love about it is that it’s almost exactly the same design as these things still are today,” she told me. “It also has mud between the teeth, in which almost certainly there may still lurk Roman nits. When I found it, it was in such good condition it looked like it had only been dropped yesterday.”

As the river meanders through the centre of the city, untold interesting stories are constantly revealed. On a small patch of foreshore in Rotherhithe in south-east London, you can see tumbled red bricks where the buildings levelled by the Luftwaffe in World War Two fell into the river. Beside those bricks are myriad rusting nails, screws and ship plates left from a time when Rotherhithe was known as a ship-breaking site in the 19th Century.

Even if I don’t find much that day, I love the peace the river brings

Nearby is a row of wooden jetty supports. Looking closely, you might notice one is somewhat different: instead of rotting from the outside, it is hollow. This post is not made of wood but is a whale rib. From the 1720s, whaling ships ferried their blubbery trophies into Greenland Dock where the whale fat could be rendered down into useful oils. Whale bones found their way into many products, but sometimes, as here, they were used whole if builders found themselves short of timber.

These items are all on a stretch of the Thames no more than 100m long.

Mudlarking is not all about the physical objects you find on the river, however. Anderson speaks poetically of the joys of being on the foreshore. “I instantly forget any anxieties or problems that I have for the few hours or so that I’m down by the river,” she said. “Even if I don’t find much that day, I love the peace the river brings – the wildlife, birds, boats going past, the sounds, the way the light reflects on the water, the changing landscape on whatever part of the Thames foreshore I happen to be mudlarking on that day. Even on a cold, windy or wet weather day, it’s very invigorating.”

But on a brisk morning, when you are up with the larks and a freezing wind is blowing along the grey Thames and no finds are turning up, it can be hard to stay cheerful. Once all I discovered was a used condom and a discarded belt. But the rich possibilities of the Thames continue to draw mudlarks back.

For Anderson, “A dream find for me would be a Neolithic flint tool… It’s lovely to find coins and things, but you can’t beat finding something like a flint tool because of [its] age and how special [it is] to find and hold. Some of them are so beautifully worked and crafted.”

Maiklem is searching for an item with a story to tell. “My dream find is a complete medieval St Thomas Becket pilgrim badge,” she said. The pewter relics were produced in huge numbers as souvenirs at Becket’s shrine in Canterbury, and you can imagine one of Chaucer’s pilgrims accidentally losing theirs on the way back into old London.

The longer you mudlark, the more you want to find. “It is addictive,” Maiklem warned me. But the bug has already bitten me – even if I do still dream of finding golden treasure in the Thames.

Unearthed is a BBC Travel series that searches the world for newly discovered archaeological wonders that few people have ever seen.

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