[6] It functions to protect surrounding towns and villages outside the Tyneside/Newcastle-upon-Tyne and Wearside/Sunderland conurbations from further convergence.
[7] This is managed by local planning authorities on guidance from central government.
A large increase to its present extent was made in 2022 when Northumberland added 26,790 hectares (267.9 km2; 103.4 sq mi).
[9] Much of the boundary is formed by local roads and land features such as rivers.
The western extent reaches 25 miles away from Newcastle, beyond Hexham and towards Haydon Bridge, becoming contiguous with the North Pennines AONB and close to the Northumberland National Park.