For generations, the reason why the Mary Rose sank during a battle with a French invasion force has divided historians.

Now a new theory can be added to the list of suggestions about why the pride of Henry VIII's navy was lost: two thirds of its crew were foreigners who failed to understand orders.

Forensic science examinations of the 16th-century crew's skulls have revealed that the majority were not British but southern European, most probably Spanish.

Researchers believe that the vessel's fate was sealed because of their inability to understand their officers' orders when it began taking on water in the Solent, off Portsmouth, in 1545.

It is believed that the crewmen were either mercenaries from the Continent recruited to fight by Henry VIII or Spanish soldiers shipwrecked penniless in Britain and forced into military service.

The new theory also goes some way towards solving the riddle of the last words reputedly shouted by the ship's admiral, George Carew, to another English ship, that his men were “knaves I cannot rule”. The latest explanation has been put forward by Hugh Montgomery, a medical researcher at University College London.

Until now, it had always been believed that the Mary Rose sank as it performed a sharp turn, causing the open gun ports to submerge, flooding the vessel.

However, Professor Montgomery claims that the ports were left open only because the Spanish crewmen could not understand quickly enough the command to close them.

He said: “In the chaos of battle, with all the shouting and guns going off, it would have taken a very clear chain of command and a very disciplined, well-rehearsed crew to close the gun port lids in time.”

He reached the conclusion after he and a team of experts carried out an exhaustive examination of the crew's remains with the permission of the Mary Rose Trust. After the skulls of 18 crew members were examined to determine where they had lived, it was discovered that about 60 per cent were of southern European origin.

Scientists can determine roughly the region where a person grew up by analysing the chemical composition of their teeth, which retain the type of water molecule they consumed in childhood.

A device called a mass spectrometer can detect whether heavy or light atoms of oxygen were present in the region's rainwater, which is absorbed into the soil and subsequently plants and people's teeth. Heavier atoms indicate a warmer climate.

Professor Montgomery said: “The analysis of the teeth rules out Britain and countries in northern Europe. It suggests that the men grew up in a warm climate, probably somewhere in southern Europe.

“It is also known that at this time Henry VIII was short of skilled soldiers and sailors and was trying to recruit mercenaries from the Continent.”

Previous experiments have revealed that the ship would have capsized if a sudden wind had sprung up as it attempted to perform a sharp turn to outmanoeuvre the French. It would have heeled, submerging the gun ports, which were open because of the ensuing battle and were only about 3ft above the waterline.

The ship was raised in 1982 after the recovery of a wealth of artefacts, as well as 10,000 human bones.

The Ghosts of the Mary Rose: Revealed is on Five at 8pm on Tuesday

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