A padlock found in a shipwreck treasure trove remained uncracked for more than 400 years until one move solved it, finally revealing its message.

The mystery surrounding the brass lock that washed ashore from the shipwrecked Ann Francis has been cracked.

Ann Francis, an Elizabethan merchant vessel, was on her way home from Spain when she ran aground during a storm on Margam beach near Port Talbot, Wales, in 1583.

Her treasure, including hundreds of gold and silver coins and one padlock, lay buried under sand for centuries before being found by metal detectorist Peter Hughes between 1996 and 2017.

Experts spent years trying to solve the code for the padlock without damaging the precious artefact.

Roughly the size of one of the ancient coins, it had letters engraved on the surface, topped with a small handle.

Specialists at the Museum Wales (Amgueddfa Cymru) where the artefact was housed and from Cardiff University joined forces to try and open the lock, which is believed to have secured a small chest of valuable items on board the doomed ship.

Eventually, a CT scan offered a solution, allowing the experts to study the mechanism inside without damaging the precious lock.

The scans allowed the teams to spot which notches matched the letters, creating a combination: ANCE.

A section of the padlock can then be pulled out, revealing a key-like item.

Dr David Williams, a researcher at Cardiff University’s Musculoskeletal Biomechanics Research Facility, said: ‘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. We normally use this technology to study bones and other biological structures, so investigating a 400-year-old padlock was certainly a first for us.’

The scientist had to wait until later in the evening for the museum experts to test the combination.

Despite the ‘satisfying’ answer, mystery still surrounds what the letter combination ANCE meant to the chest’s owner.

Elizabethan combination locks have been found in Britain before, but it is rare to find one that is in ‘exceptionally’ good condition and linked to a dated shipwreck, senior curator Alastair Willis from Museum Wales said.

‘Of course, now we’ve solved it, we are left wondering if the code meant something to its owner,’ Alastair said.