The Wealden heathlands once covered an extensive area on the sandy soils of western Surrey. A combination of urbanisation, and neglect leading to woodland colonisation, has taken a severe toll, with relatively few good sites now left. The best of these remaining few undoubtedly Thursley, largely protected as a National Nature Reserve covering 325ha (just over 800 acres). It lies about 5 miles north of Haslemere, in the area where most of Surrey's heathy commons are concentrated.