Archaeologists at Cambridge have unearthed one of Britain's largest hospital burial grounds in their own bak yard.

More than 400 graves were discovered under the Old Divinity School at St John's College and found perfectly preserved skeletons from the 13th-15th Centuries as well as ‘fragmentary remains’ of around 1000 people.

The graves are of those treated at the medieval Hospital of St John the Evangelist which stood opposite the graveyard until 1511 and where the college takes its name from.

The skeletons are of people who died between the ages of around 25 and 45 - although none of which are children or young women.

Details of the dig have only emerged today in a new report despite the dig happening between 2010 and 2012 during a refurbishment of the Victorian building.

The report suggests that the hospital was not for medical treatment, rather spiritual and physical care.

Craig Cessford, of the Cambridge University Department of Archaeology and Anthropology, said:  ‘This is certainly the biggest medieval burial site in Cambridgeshire and one of the largest excavations in Britain.’

The team, from the Cambridge Archaeological Unit, found the burial ground to have six "cemetery generations".

Generations are defined as the time taken to fill all available space before burying other bodies in the same locations.

The 1,300 estimated bodies which were buried in neatly laid-out rows, or deposited in a charnel house on the site.

Of the human remains excavated, 400 individuals were closely analysed to discover clues as to what went on in the cemetery and the community at the time.

From those, it appears the bodies did not show signs of serious illnesses or conditions that would have required medical attention.