St Cross — one of Oxford's oldest churches — is set to be taken over by Balliol to house the college's historic collections.

After more than 800 years of Christian worship, St Cross is unlikely to continue as a full time church after tomorrow.

Dwindling congregations at the small church, which dates from 1180, are being blamed.

Tomorrow a service of thanksgiving will be held at St Cross, conducted by Canon Brian Mountford, who is also the vicar of the University Church of St Mary the Virgin in High Street.

The Church Commissioners are still to respond to an application from the Oxford Diocese that would allow Balliol to go ahead with its plans.

But they are expected to give approval in the winter.

The Master of Balliol, Dr Andrew Graham, said: “St Cross Church is one of the oldest buildings in Oxford.

"Balliol is possibly the oldest college in the English-speaking world with archives to match — certainly the oldest on its original site. Bringing these together and combining them with state-of-the-art conservation facilities so that scholars from around the world will be able to consult Balliol’s archives and historic collections will represent a unique and long-lasting contribution both to heritage and to scholarship. "

Balliol plans to spend £3m to restore the building and transform it into a Historic Collections Centre, where the college's treasures will be put on public display.

College archivist Dr John Jones said the collection included 400 medieval manuscripts of international importance. Among its treasures are the library of William Gray, Bishop of Ely, described as the finest private collection from the Middle Ages.

The church, which is next door to Balliol's Holywell Manor graduate centre, will remain consecrated, and it is hoped occasional services will still be held in the chancel.

The site contains one of the most impressive small cemeteries in England. Famous literary figures buried there include Wind in the Willows author Kenneth Grahame.