Researchers decode code in 16th-century Welsh shipwreck padlock

Experts have decoded a four-letter combination that opened a brass padlock recovered from a 16th-century shipwreck off the Welsh coast, using micro-CT scans to examine its mechanism without dismantling it.

The lock was found by metal detectorist Peter Hughes near Margam, in Port Talbot, in 1999. It was part of a hoard from the Ann Francis, a ship caught in a storm on 28 December 1583 while returning from Spain.

Researchers from Amgueddfa Cymru and Cardiff University identified the code as ANCE. The lock has four rotating rings, each bearing six letters, giving 1,296 possible combinations.

A puzzle revealed by scanning

David Williams, a Cardiff University engineering research associate, said the scanning equipment was not designed for the task. The team made three scans, changing its approach after the second went wrong; the final scan revealed how the letters aligned.

Hughes said he had spent about 20 years trying unsuccessfully to open the lock. He passed the wider collection to Amgueddfa Cymru in 2017. The artefacts, including the padlock, went on display at Swansea Waterfront Museum in July 2026.

Curators believe the lock may have secured the Spanish silver coins found nearby or a small chest containing valuable items. They do not know what it protected. The lock remains in excellent condition and still works as it would have centuries ago, senior curator Siân Iles said.