Skeletons discovered in a mass grave close to Durham cathedral are the remains of Scottish prisoners of war - with some as young as 13 years old, experts have revealed.

Researchers from Durham University identified the bones as coming from soldiers captured after the Battle of Dunbar in 1650.

It was one of the bloodiest battles of the 17th century's Civil Wars, when Oliver Cromwell's troops won an unexpected victory against Scottish supporters of Charles II.

The Dunbar prisoners - aged predominantly between 13 and 25 - were taken south to Durham Castle, now part of a Unesco World Heritage site, where around 1,700 died of malnutrition, cold or disease after the 100-mile march.

Grim end: Skeletons (pictured during excavation work) discovered in a mass grave close to Durham cathedral are the remains of Scottish prisoners of war, experts have revealed

In November 2013, archaeologists began work on the remains, which were found during work at Palace Green, close the the city's cathedral.

Archaeologists at first thought they had uncovered remains of Durham Cathedral's medieval cemetery, the boundaries of which may have extended further than the present day burial site.

But the corpses had been tipped into the earth without elaborate ceremony, suggesting they were part of a mass burial.

Archaeologists at first thought they had uncovered remains of Durham Cathedral's medieval cemetery, the boundaries of which may have extended further than the present day burial site (remains pictured)

Puzzle: The corpses had been tipped into the earth without elaborate ceremony, suggesting they part of a mass burial (Durham University expert analysing the bones pictured)

The Dunbar prisoners were taken south to Durham Castle, now part of a Unesco World Heritage site, where around 1,700 died of malnutrition, cold or disease after the 100-mile march. The multiple lines seen on these teeth - known as enamel hypoplasia -suggest this male aged 18-25 years suffered poor nutrition and illness

THE BATTLE OF DUNBAR: ONE OF THE CIVIL WAR'S BLOODIEST MOMENTS Following Parliamentary victory in the first and the second Civil Wars, Charles I had been executed in January 1649 and a Commonwealth declared in England. In June 1650 his son landed in Scotland, where he was proclaimed King Charles II. In July the English Parliament, expecting Charles to initiate a Scottish led campaign for the English crown, launched a pre-emptive invasion of Scotland. Following the battle, Cromwell was able to march to Edinburgh where he eventually captured the capital following the defeat of the castle. Prisoners were force-marched towards England, to prevent any attempt at rescue, and imprisoned in Durham Cathedral (Cromwell at Dunbar, painted by Andrew Carrick Gow pictured) Ten thousand men and 5,000 horses from the New Model Army was sent north under the command of Oliver Cromwell. Scottish forces numbering 25,000 were raised in response, under General Sir David Leslie. Leslie fought a defensive campaign about Edinburgh, avoiding a pitched battle. The New Model Army was transported by sea via the port of Dunbar. Having failed to bring Sir Leslie to battle they were forced by the weather, sickness and supply problems, to retire to Dunbar, first in early August and then again in late August. Sir Leslie, outnumbering the New Model two-to-one, saw his opportunity and marched around Dunbar to cut Cromwell's road connection to the border fortress of Berwick. Cromwell now finally had Leslie offering battle, but his New Model Army was at a severe disadvantage. Despite this, rather than evacuate by sea, Cromwell met the challenge, achieving what was arguably the most dramatic victory of the Civil Wars. Following the battle, Cromwell was able to march to Edinburgh where he eventually captured the capital following the defeat of the castle. Prisoners were force-marched towards England, to prevent any attempt at rescue, and imprisoned in Durham Cathedral. Conditions on the march and in the prison were terrible. Of the reported 6,000 prisoners, 5,000 were marched south resulting in the loss of 2,000, a further 1500 dying whilst in captivity and the majority of the survivors sold into slavery. More died as a result of capture than on the battlefield. Sources: The Battlesfield Trust/Historic UK Advertisement

Richard Annis, senior archaeologist with Archaeological Services Durham University, said at the time: 'We have found clear evidence of a mass burial and not a normal group of graves.

In November 2013, archaeologists began work on the remains, which were found during work at Palace Green, close the the city's cathedral, for a new café

'One of the densest areas of the excavation was further north, which is further away from the edge of the presumed graveyard.

'The bodies have been tipped into the earth without elaborate ceremony and they are tightly packed together and jumbled. 'Some are buried in a North-to-South alignment, rather than the traditional East-to-West alignment that we would expect from a conventional medieval burial site.'

Radiocarbon tests on the jumbled remains of between 17 and 28 people has led to the conclusion that they were Scottish soldiers aged between 13 and 25.

Researchers at Durham University concluded that the identification of the remains as the Dunbar prisoners was 'the only plausible explanation' when scientific data was analysed alongside historical information.

The Battle of Dunbar was one of the most brutal, bloody and short battles of the 17th century civil wars.

In less than an hour the English Parliamentarian army, under the command of Oliver Cromwell, defeated the Scottish Covenanting army who supported the claims of Charles II to the Scottish throne.

Past life: It isn't just skeletons that have been unearthed at the site. Archaeologists have also discovered artefacts suchas this pipe, which would have been used in the 17th century

Although the exact figures are not known, it is thought that around 1,700 Scottish soldiers died of malnutrition, disease and cold after being marched over 100 miles from the South East of Scotland to Durham, where they were imprisoned in Durham Cathedral and Castle, by then disused for several years.

Richard Annis said: 'This is an extremely significant find, particularly because it sheds new light on a 365-year old mystery of what happened to the bodies of the soldiers who died.

'Their burial was a military operation: the dead bodies were tipped into two pits, possibly over a period of days. They were at the far end of what would have been the Durham Castle grounds, as far as possible from the Castle itself - they were out of sight, out of mind.

Lifestyle: Distinctive markings on skeletons have given away secrets about the soldiers' lifestyles. Here the uniform teeth marking (ringed) suggests this man was avid pipe smoker

'It is quite possible that there are more mass graves under what are now university buildings that would have been open ground in the early to mid-17th century.'

Archaeologists have also been given a glimpse into the lifestyles of the soldiers who were unceremoniously buried in the unmarked grave.

Tooth and bone analysis has revealed that many men suffered malnutrition and illness during childhood.

The tell-tales marks of smoking have also been observed - circular holes where clay pipes wore down teeth.