Mudlarking: Pirates of the River Thames

thames river pirate treasure

By Jason Sandy

As you look across the quiet, serene river today, it’s hard to imagine the vast sea of ships which once clogged the Thames. By the 18th century, London had become the largest and most important port in the world. Thousands of ships entered the port each year, carrying goods and produce from around the globe. 

The long process of paying custom taxes and unloading the cargo into warehouses meant that ships sometimes waited up to three months on the river, causing a gridlock and preventing the free movement of other ships. Statistician Patrick Colquhoun estimated that at the end of the 18th century there were 8,000 vessels on a six-mile stretch of river around London Bridge. He calculated that the amount of property floating on the river at any one time was worth approximately $96 million in today’s dollars. The valuable cargo attracted pilferers and river pirates who targeted and plundered the vulnerable ships. Colquhoun estimated that over $640,000 of goods (a staggering $58.7 million at today’s rates) were stolen in 1797. Because of the great financial losses caused by piracy, the Thames River Police was established in 1798 in Wapping (London) as the first organized police force in the world.

Once river pirates were captured, they were tried and imprisoned in Marshalsea or Newgate prisons. Pirates who were captured abroad were also brought back to London and tried by the High Court of the Admiralty. If the pirates were condemned to death, they were transported in a cart and paraded across London Bridge so everyone could see them as they travelled to Execution Dock in East London, which was used for over 400 years to execute pirates, smugglers, and mutineers. 

Shortly before an execution, crowds would gather along the river bank or watch from boats on the Thames to get a better view of the hanging. To prolong the agony, pirates would be hung from a shortened rope (so it didn’t break their necks) over the tidal river at low tide. If the pirates didn’t die by slow asphyxiation, they would drown as the incoming tide submerged them. The corpses were customarily left for three tides before they were cut down. Captain Kidd was probably the most infamous pirate to be hung at Execution Dock. As a warning to incoming ships and pirates sailing up the Thames, some of the corpses were tarred and hung at the entrance into London from the sea. It must have been a pretty gruesome sight!  

pirate cob coin

Although river pirates disappeared centuries ago, still today we find traces of their former existence. Mudlark Mike Walker has discovered numerous “pirate cob” coins of various shapes and sizes while mudlarking at low tide along the exposed riverbed of the Thames. To expedite the transport of precious metals from the South American colonies back to Spain, mints produced irregular coinage called “cobs.” Rough chunks of gold, silver and copper were cut to the appropriate weight and struck with crude dies. The coins varied greatly in size, shape and impression and were often disfigured with large cracks and imperfections. In the 16th and 17th centuries, pirates ransacked many Spanish galleon ships on their way from the Caribbean to Spain, seizing their cargo of coins. Some of the Spanish cobs made their way back to London as illustrated by this copper Spanish 8 Maravedis cob coin dated 1652 that was found in the River Thames by Mike Walker. 

pieces of eight

Other coins from various Spanish American colonies have also been found in the River Thames. Mudlark Oli Clark found a Spanish 1/2 Reale coin minted in Mexico and dated 1781. Often referred to in pirate folklore as “Pieces of Eight,” a silver Spanish 8 Reales coin was found by mudlark Nick Stevens (below right). Possibly plundered from a Spanish ship and brought back to London, this large 8 Reales coin is very unusual because it has been re-milled and re-circulated as a King George III Bank of England dollar (five shillings) coin dated 1804.

river thames execution token

The last hangings at Execution Dock took place in 1830, but evidence of the infamous dock can still be found on the riverbed at low tide. While mudlarking in East London, Steve Brooker found a rare 17th century trade token stamped with the words “Execution Dock.” Worth a farthing, this trade token was issued by John Shaw for his business located at Execution Dock in the 17th century. As one can imagine, shops took advantage of their prime location when crowds gathered to watch the gruesome events. 

thames river gallows coin

Several years ago, Steve Brooker also found a copper coin dated 1677, which was purposely rubbed smooth and hand-carved with an illustration of the gallows. I wonder if a condemned pirate created this token as he awaited his certain demise at the gallows?

If the river pirates were not condemned to death, they were thrown into prison with other criminals. In the 18th century, London’s prisons were massively overcrowded. As a result, the government began converting decommissioned warships into floating prisons called “hulks” on the River Thames. Some prisoners were locked up on the ships until space could be found on a convict ship bound for Australia, but many prisoners served their entire sentence on the hulks floating on the Thames. While on the boat and at work, the prisoners were shackled to prevent escape.

ball and chain

In 2009, mudlarks Rick Jones and Steve Brooker thought they had found a large cannon ball until they picked it up and a chain slithered out of the Thames mud, still attached to an iron bal dating from the 1700s or early 1800s. Kate Sumnall, a curator at the Museum of London, said: “The river is the repository for so many of London’s stories, and this extraordinary find gives us a tantalizing glimpse of the human trials and tribulations of past Londoners. Whether a would-be Houdini freed himself from the great iron on his leg, or perished in shackles, or whether this ball and chain was simply discarded, we can never know.” When I found a 17th century key near Execution Dock a couple of years ago, I wondered if it had been used to lock the shackles of a prisoner.  

thames river antique key

These incredible artifacts discovered on the exposed riverbed of the Thames provide an interesting insight into the lives, imprisonment, and execution of pirates when London was the largest port in the world. To commemorate Execution Dock, a replica of the gallows has been built on the riverbank in front of the Prospect of Whitby pub in East London. As a result of river pirates on the Thames, the first police force in the world was established, and the maritime police unit is still located on the same spot along the River Thames. Today they continue patrolling the river as they did back in the 18th century.

Mudlarking on the Thames Foreshore requires a permit. Learn about rules for mudlarking in London ›

Get a peek at some of London mudlark Jason Sandy's collection

Learn more about mudlarking


Learn more about the experiences of mudlarks, who search the shores of rivers, bays, and seas for historical finds and other objectsArticles ›

This article appeared in the Beachcombing Magazine January/February 2019 issue.


I have been a beach comer for 25 years . I have some pieces I would love to see if someone can give them a name .

Brenda Pettipiece July 20, 2022

All these amazing discoveries are so exciting!! I would love to mudlark; what a satisfying hobby.

Victoria Richardson March 21, 2022

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