This is a really interesting question and one that was recently raised by PropertyChecklists.co.uk here. Most of us perceive it to be beautiful and undulating countryside which is protected from building on at all costs. But, this is not the case and the Green Belt can include power stations, hospitals and schools for example. Designated as such in the 1930s, the Green Belt was intended to stop cities merging and encroaching on the countryside. England has around 1.6 million hectares of Green Belt and this is in addition to protected areas such as National Parks and Areas of Outstanding Natural Beauty. According to the government’s National Planning Policy Framework, the purpose of the Green Belt is; to check the sprawl of large built-up areas, prevent towns merging, safeguard the countryside, preserve the character of historic towns, and encourage the recycling of derelict and other urban land. While development considered harmful to the Green Belt should not be approved, there are exceptions such as limited infilling in villages, limited affordable housing for local community needs. Each year, between two and three per cent of new homes are built in the Green Belts in England. Read the article here.