Scientists Used CT and Finally Opened a 400-Year-Old Lock From a Welsh Shipwreck

Scientists used CT scans to crack an Elizabethan lock that resisted decades of attempts.

For nearly 20 years, Peter Hughes tried to open a tiny brass padlock he had found buried in the sand on a Welsh beach. Its four rings, each engraved with six letters, still turned smoothly. But no matter how he arranged them, the lock refused to open. After all, there were 1,296 possible combinations.

Even long before Hughes came across the lucky find, the padlock had already kept its secret for more than four centuries. It came from the Ann Francis, a merchant ship wrecked off the coast of Wales in 1583, possibly while carrying a small fortune in silver and gold.

Now, researchers at Cardiff University and Amgueddfa Cymru–Museum Wales have finally cracked its code. Instead of trying all the possible combinations and cracking it by brute force, they used a sophisticated CT scanner to peer inside the mechanism without damaging it.

The correct combination proved to be ANCE.

But what was the lock protecting, and what did those four letters mean to whoever owned it?

A 16th-Century Lock Meets 21st-Century Technology

At first glance, the lock resembles a miniature ancestor of a modern combination padlock. Each of its four rotating rings carries six letters. The device also has letters engraved on stationary sections at either end, apparently designed to confuse anyone attempting to guess the code.

Hughes discovered the lock in 1999, among hundreds of objects he recovered from Margam Beach, near Port Talbot.

“I tried to unlock it for about 20 years, I tried moving the dials, finding the right combinations, and I failed,” Hughes told BBC News.

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Sure, you could go through all 1,296 possible combinations one at a time, but the lock had seen better days. Repeated attempts risked damaging the delicate mechanism. Grit had accumulated inside, and forcing the rings could cause wear. Museum specialists needed another approach.

They turned to David Williams, a researcher at Cardiff University’s School of Engineering who normally uses micro-computed tomography (micro-CT) to examine bones and biological tissues.

Much like a hospital CT scanner, the equipment takes X-ray images from multiple angles to reconstruct an object’s interior. Micro-CT works at a much smaller scale, revealing fine structures hidden inside compact objects.

“We did a first scan to see if we could see anything and we were quite surprised that we could see letters,” Williams told the BBC.

The second scan went badly. On their third attempt, the researchers adjusted their approach and obtained images detailed enough to identify the internal notches that controlled the lock.

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“By creating a detailed 3D image of the internal mechanism, I could see how the notches lined up with the letters and identify the exact combination,” Williams said.

Back at the museum, curators carefully aligned the rings to spell ANCE. The mechanism loosened, and the key-like internal component slid free.

After 443 years, the lock had finally surrendered its secret.

A Smuggler’s Ship and a Lost Fortune

According to research published by Museum Wales, the Ann Francis belonged to Francis Shaxton, a merchant from King’s Lynn, England. Shaxton and his father, also named Francis, were notorious smugglers who operated a fleet of trading ships.

In October 1583, the Ann Francis sailed to Spain carrying wheat. Its return cargo included payments in gold and silver, some of which had originated in Spain’s American colonies.

But on December 28, a violent storm drove the ship onto Margam Beach, far from its intended route home.

The wreck quickly attracted looters. Historical court records describe a dispute over the salvaged cargo, with one landowner accusing more than 100 people of plundering the vessel.

An inventory from the time listed cannon, anchors, spices, money and three chests with broken locks.

Could the newly opened padlock have belonged to one of those chests? Possibly, although nobody can establish that connection with certainty.

Beginning in 1996, Hughes spent 21 years searching the beach whenever storms and dredging exposed fresh material. His discoveries included approximately 870 gold and silver coins, navigational equipment, cooking utensils and personal belongings.

Some coins came from Germany and Portugal. Others were minted in Mexico, including remarkably early examples of Spanish colonial coinage.

The padlock was found among Spanish silver coins and near two weights once used to check the value of gold currency.

Perhaps it protected coins. Perhaps it guarded valuable documents or textiles that disintegrated centuries ago. We’ll likely never know.

The Mystery That Remains

The lock itself is a quite rare piece of 16th-century technology. Similar devices, sometimes called Nuremberg locks, circulated in Elizabethan Britain. One example in the British Museum from the period, for instance, opens with the letters MARCI.

What makes the Ann Francis lock exceptional is its preservation and its connection to a shipwreck with a precisely documented date.

Unlocking it also allowed conservators to remove accumulated grit, helping prevent further deterioration.

As for the chosen combination ANCE, researchers have found no explanation. It could have held a personal meaning for its owner, or simply been a convenient combination.

“Of course, now we’ve solved it, we are left wondering if the code meant something to its owner,” said Alastair Willis, senior curator at Museum Wales, in the museum’s announcement.

The lock is now displayed alongside the ship’s surviving treasure at the National Waterfront Museum in Swansea.