Green Belts were made possible by the Town and Country Planning Act 1947 but the Oxford Green Belt was not formally approved until 1975. The original designation of the Oxford Green Belt was to prevent the city from extending further into the countryside. The role of the Green Belt within the surrounding districts was to preserve the rural setting of the city. This was the context in which the boundaries of the Green Belt were set in South Oxfordshire through the local plan process.
The National Planning Policy Framework (NPPF) states: 'The fundamental aim of Green Belt policy is to prevent urban sprawl by keeping land permanently open; the essential characteristics of Green Belts are their openness and permanence.' Green Belt serves five purposes:
to check the unrestricted sprawl of large built-up areas;
to prevent neighbouring towns merging into one another;
to assist in safeguarding the countryside from encroachment;
to preserve the setting and special character of historic towns; and
to assist in urban regeneration, by encouraging the recycling of derelict and other urban land
The NPPF also states that the permanence of Green Belts is an essential characteristic (and advises that, 'once established, Green Belt boundaries should only be altered in exceptional circumstances, through the preparation or review of the Local Plan. At that time, authorities should consider the Green Belt boundaries having regard to their intended permanence in the long term, so that they should be capable of enduring beyond the plan period.'