He was found lying on his front, head twisted to the side. One arm was bent above his head, suggesting he had fallen – or perhaps had been pushed – to his death in the river more than five centuries ago.

But aside from his puzzling position, the skeleton discovered this year near the shore of the Thames in London was notable for another, very particular reason. Though his clothes had long since decayed, on the man’s feet were a pair of remarkably well preserved – and extremely rare – knee-high leather boots. Might they hold clues, archaeologists wondered, to who the man was and, just possibly, how he died?

The mystery of the man in the medieval wellies was uncovered in Bermondsey by archaeologists working on the Thames Tideway tunnel, the so-called “super-sewer” currently being built to update the capital’s Victorian sewage network.

The boots during the conservation process. Photograph: MOLA Headland Infrastructure

It’s not unusual to find bodies on the foreshore, but the style and preservation of the man’s footwear, made of leather “quarters” stitched together with waxed flax thread, is exceptional, say archaeologists.

“Leather can be very well preserved in London, especially if it’s found in a ditch that would have been full of water, or near the riverfront,” said Beth Richardson, a finds specialist for the archaeological team from Mola Headland Infrastructure. In the absence of any metalwork or other dating evidence, the style of the boots – unheeled, with a single, flat sole reinforced with “clump soles” at the front and back – dated the skeleton to the late 1400s or early 1500s at the latest.

“But what is unusual about these boots is that we never find high boots like this – they are always shoes or ankle boots,” Richardson said. “High boots are just not very common throughout medieval times, and actually [during] Tudor times and the 17th century as well. If you look at pictures or illuminated manuscripts or portraits, very few people are wearing boots.”

The fact that they reach the knee makes it likely the boots were waders, experts think, making it possible the man worked in or around the river as a dock worker, mudlark or fisherman. Mariners of the time were known to wear long boots, according to Richardson, as evidenced by the large number found on the wreck of the Tudor warship the Mary Rose.

And like their modern-day welly-boot equivalent, they are nothing fancy. “These were very simple boots,” says Richardson. They are not fashionable at all, they haven’t got buckles or anything like that – they are just practical, everyday boots.” Conservation work to preserve the leather is still ongoing, and there is no immediate plan to put the boots on display.

Plant matter found inside the boots is yet to be analysed, but the archaeologists suspect it was a lining of moss that had been added to keep the man’s feet warm as he waded.

Even without his distinctive footwear, however, there are clues to his identity. Evidence of extensive degenerative joint disease along his spine and left hip joint show he lived a physical life and would have suffered pain every day, according to Niamh Carty, an osteologist. Though she could not rule out that he was younger than 35, she believes he was probably much older.

In addition, the man has distinctive grooves in his teeth, “a possible indication of pulling some sort of material over the biting surface of the teeth or holding an object in the teeth for prolonged periods of time,” said Carty. One possibility is that he was pulling rope between his teeth, as a fisherman might.

As for how the man came to die, we will never know for sure, but there is no evidence of foul play, according to the archaeologists.

“He may have been working in the river and the tide got too much for him, he may have fallen over, he may have been tired,” Richardson said. “He may have had too much to drink. We really don’t know.”