For 1,000 years Oxford Castle has occupied a five-acre site in the heart of Oxford. The castle was originally built by Robert D'Oilly, friend to William the Conqueror and has been home to kings, sheriffs and, latterly, convicts. For 900 years Oxford Castle was used for a Prison, cut off from the rest of the city. As a Castle, the walls kept people out and later, as a prison, they kept people in, so that the site has never been open to the public before, until now.

The Oxford Castle Heritage Project began in 1997 when Oxfordshire County Council purchased the freehold of the castle site from the Home Office, when the HM Prison closed. The site included several Scheduled Ancient Monuments, Grade I, Grade II* and Grade II listed buildings and structures, and included the two oldest remaining structures in Oxford – St George's Tower and the Castle Mound. The right for the Council to acquire the site had been retained in criminal justice legislation in the 1970's, largely due to the efforts of Hugh Merscy Walton who was at that time solicitor to the Council and subsequently a trustee of Oxford Preservation Trust.

Oxford Castle first appears in the OPT's Annual Report of 1942: "Great expectations have been aroused recently by the prospect of Oxford Castle and Prison being vacated….and the possibilities for the site…as a space..for a public park, perhaps a County and City museum". There were several further rumours of the prison closing, so that when it did happen in 1996 various organisations and individuals had hopes of using the site for uses including a concert hall, museum of military history, and student housing.

The County Council's ambition was to see the site re-used and regenerated. It set out clear project objectives, in spite of property consultants advice that "there could be no alternative uses for Oxford Castle with any positive value…. the site is a liability…."

The objectives were:

• to restore and conserve the historic buildings
• to maximise public access to and through the site and to as many of the buildings as possible
• for the whole site to be developed, managed and recognised as a single entity
• to encompass sustainable commercial use as well as a full interpretation of the site's history and heritage and good provision for education
• to be delivered at minimum risk and cost to council tax payers