The London green belt was originally envisaged in the late 19th century as an amenity for city-dwellers rather than a cordon sanitaire to protect the rural. Though the Ringstrasse of Vienna and the parkways of Washington are sometimes cited as inspirations, the "green girdle" proposed for London was to be placed much further out, beyond the working class districts, rather than between the elite-dominated centre and the peripheral industrial areas. The aim was to improve the health of the working classes, rather than isolate them, through access to fresh-air and exercise, and was given political impetus when recruitment during the Boer War revealed poor levels of fitness among the urban poor, prompting a Parliamentary Committee on Physical Deterioration in 1903. This reinforced existing concerns over national decline (arising from the advance of the USA and Germany) and would provide a background hum to the Liberal government's welfare reforms after 1906, including the Housing, Town Planning, &c. Act 1909, which banned "back-to-backs" and required local authorities to draw up town plans.
The green belt was a progressive cause, but one more influenced by the eugenic concerns of the Fabians (improve labour) than the bucolic socialism of William Morris (improve life). It also found common cause with conservatives worried more about "racial decay" than rural preservation. As a practical policy it went hand-in-hand with slum clearance and quality public housing, hence it was championed by the likes of Herbert Morrison's LCC in the interwar years, leading to the Green Belt (London and Home Counties) Act 1938, which empowered local authorities to buy land to be kept free from development. This public health focus was reinforced in the 1940s by a renewed desire, occasioned by wartime rationing, to maintain agricultural land close to the city to provide fresh food. However, this also marks the transition in the concept of the green belt from an urban resource to a strategic resource in its own right. Green belts were formalised nationally in the Town and Country Planning Act 1947, which also provided the foundation for the modern system of planning controls.
From the 50s through the 70s, urban populations were partially decanted to new towns as the old city slums were cleared, with the green belt providing a way of ensuring that the likes of Harlow and Stevenage developed as distinct centres rather than just exurban sprawl in the US manner. It is during this postwar period that the idea of the green belt as a restraint, rather than an urban amenity, takes hold, both in the sense of containing the social ills of inner-cities (increasingly associated in the popular imagination with Commonwealth immigrants) and isolating the decanted working classes in the often under-equipped new towns. The implementation of green belts became government policy (i.e. a central push rather than a local authority pull) in 1955 under the Conservatives, marking the inflexion point in attitude. The era also saw a significant improvement in urban health, due to the clean air acts and the spread of indoor plumbing, while mechanisation reduced the population of farm-workers. These developments replaced the old social dichotomy of unhealthy city and healthy countryside, embodied in the pasty-faced street urchin and the ruddy-cheeked farmer's child, with an aesthetic distinction of the built environment: the glass and concrete city and the increasingly faux-rural exurbs.
In the 1980s, the value of the green belt as an urban "lung" continued to decline as deindustrialisation reduced pollution, while the growth of imported foodstuffs reduced the land's agricultural utility (if not its market value). As the health and recreational justifications of old lost their weight, the cause of environmental protection gained prominence, encouraging the idea that as the green belt was a good in itself it should be expanded where possible. In fact, much green belt land is of no more ecological value than an urban brownfield site (and sometimes less). The consequence is that the land designated as green belt has more than doubled in size since 1979 and now accounts for 13% of the total land in England. In contrast, only 10% of land is developed (which includes roads and urban green spaces), while national parks account for 9%. That the last 30 years have seen persistent political pressure to expand the green belt (and simultaneously improve transport links) indicates that its main purpose had become that of a low-density housing zone for wealthier urban workers and the site of a growing professional services economy.
The London green belt is now over 5,000 square kilometres in size, which means that it is three times as big as the urban area it surrounds. This is enough space to build as many homes as already exist in the entirety of the UK at current densities: around 27 million. 7% of the London green belt is made up of golf courses, which means that surrendering half of them would provide enough land for 1 million new homes. It is estimated that there is enough developable land within 1 mile of existing railway and Tube stations, and within 60 minutes journey time of Central London (a radius of 90km), to build 2.5 million new homes. 22% of the land within the GLA boundaries is green belt, which constitutes an area large enough to support 1.4 million additional homes. Having declined from 8.2 million to 6.6 million between 1951 and 1981, the population of the capital bounced back to 8.2 million in 2011 and is expected to exceed 9 million by the time of the next census in 2021.
The idea of the green belt as an "interzone" between city and country has long gone. Improvements in transport have pushed the commutable boundary much further afield (Crossrail is designed to serve the green belt as much as the metropolis). At the same time, improvements in communication have amplified the value of agglomeration in city centres, leading to the growth of global hubs, such as the City. The consequence in London is the emergence of concentric rings of wealth, the inner boroughs and the green belt, sandwiching a ring of outer boroughs with an increasingly low-paid "service" population. The Tory plan to extend right-to-buy to housing associations, and require further council sales to fund the promised discounts, will exacerbate this by reducing the remaining pockets of social housing in the inner boroughs. The inner city is increasingly the inner-outer city, to be found in Mitcham and Leyton rather than Brixton or Bethnal Green. Gradually, London is replicating the social geography seen in New York and Paris.
The historic irony is that a legacy of early nineteenth century pro-social reform and mid-century central planning became a key tool for the protection of class interests antagonistic to the poor and the state. This is nowhere more obvious than west of London, specifically the area bounded by Reading, Slough, Heathrow and Bracknell. One objection to the expansion of Heathrow Airport is that it would take a nibble out of the green belt. A more ambitious plan would see the entire area developed, centring on the corridor of the M4. Of course, this would mean development around Windsor and Eton, which appears to be a no-go for some strange reason (maybe something to do with Legoland). Compare and contrast with the long-standing government encouragement for development east of London, the so-called Thames Gateway, which covers an area of significantly greater ecological value along the banks of the Thames estuary.
The obvious conclusion is that not all parts of the green belt are equal, which appears to be the position of its modern defenders to judge by their willingness to countenance land-swaps. According to Simon Jenkins: "Those of minimal amenity value would be released in favour of belt extension elsewhere. It is stupid to guard a muddy suburban field while building over the flanks of the Pennines". Despite the reference to ancient limestone, this attitude clearly reflects on the social value of land as a commodity rather than the intrinsic value of the natural environment, hence the paradigm of trade and stock management. By "amenity" I suspect Jenkins means the outdoor pursuits of the middle-classes, though he probably has fell-walking and horse-riding in mind rather than paint-balling or golf, which is an echo of the "improving" visions of the Edwardians who rhapsodised about Sunday school trips to a bluebell wood.
Jenkins has long insisted that the UK's housing crisis is a problem of poor urban resource management, and thus implicitly of selfish townees. There is some truth in this, however it is easy to fall into the trap of assuming that the solution to an urban problem lies within the urban area, and to in turn assume that "urban" and "green belt" are mutually-exclusive. This is to continue the thinking of the late twentieth century and see the green belt as a check on the ill-discipline of the city. For example, under-occupancy is often discussed as a urban issue, in the context of the bedroom tax and foreign investors, but empty rooms are more common in owner-occupied properties in the green belt. The structural causes of the under-provision of housing are not limited to cities, let alone London: regressive property and inheritance taxation; high land prices and no penalties on under-use (which leads to land-banking); and a cartel of private builders with insufficient competition from local authorities.
The solution to the housing crisis, particularly in London, requires us to return to a view of the green belt as a resource for the city, not a restraint. This doesn't mean throwing up a couple of million homes willy-nilly around the M25, but expansion along the axial transport corridors that already exist to Reading, Crawley, Luton and Southend. This would be a return to the development pattern that predated the postwar green belt, with houses and light industry following first the railways and then the new arterial roads. The green belt also provides the opportunity to build a high-speed orbital rail line linking London's airports and reducing traffic through the city centre, but given the political trouble that relatively small-scale incursions into the green belt like Heathrow and HS2 have produced, the suspicion is that wholesale reform will continue to nestle in the long grass. That both leading candidates for the London mayoralty, Sadiq Khan and Zac Goldsmith, are on record as considering the green belt "sacrosanct" is not encouraging. We're not protecting nature, we're merely privileging property.