London Mayor Sadiq Khan’s surprise announcement this week that he will “actively explore” building homes on parts of London’s protected green belt land marks a dramatic policy reversal that has surprised and shocked city planners.
Breaking what he called “longstanding taboos” to address “the most profound housing crisis in the capital’s history,” Khan unveiled an ambitious target of one million new homes in the next decade—requiring construction at nearly triple the current pace. This proposal comes at a time when the entire system of longstanding protections over the Green Belt and inner London’s Metropolitan Open Land have come under question from the Labour Party at borough, regional, and national levels.
What Are London’s Green Belt and Metropolitan Open Land?
To understand the significance of this proposal, it’s important to know what London’s green belt is – and its sibling designation, Metropolitan Open Land (MOL), which protects green space within London’s urban area. The Metropolitan Green Belt around London is part of a national policy, dating back to the mid-20th century, that surrounds the metropolis with a wide ring of mostly undeveloped land. The core idea (formulated by planners like Sir Patrick Abercrombie during World War II) was to prevent urban sprawl – stopping London from endlessly expanding and merging into surrounding towns.
London’s green belt was established in the 1950s as a ring roughly 7–10 miles deep encircling the capital. It includes parts of counties all around Greater London. Development in the green belt is heavily restricted by national planning rules: new buildings are generally not allowed except in very special circumstances. By design, the green belt is largely made up of privately-owned land – much of it farms, woods, golf courses, and low-density uses – rather than formal public parks.
Within Greater London’s boundaries, there is a separate but analogous designation: Metropolitan Open Land. MOL was created to protect significant open spaces inside the built-up area of London that are important to Londoners. In planning terms, MOL enjoys “equal legal status” to the green belt – the protections are essentially the same, just applied inside the city. Much of London’s large parks, heaths, and commons are designated as MOL.
Both the green belt and MOL aim to curb development, but their rationale includes more than just blocking housing. They are meant to guide where growth goes (encouraging regeneration of derelict urban land) and to safeguard space for nature and recreation. Until now, Sadiq Khan himself had repeatedly vowed to defend both designations – which is why his new openness to building on green belt land marks such a dramatic policy shift.
Is the Green Belt Really “Green” – and Does the Idea Still Work?
One of the flashpoints in this debate is whether London’s green belt today truly serves its intended purpose – and whether all that land is genuinely “green” open space worth saving. Mayor Khan has argued that much of it is not. “People will assume that all green belt is green and pleasant, is rich in wildlife… That is not the case,” he said, noting that “a lot of it is poor quality, badly maintained, and inaccessible to Londoners.”
A striking statistic underlies his claim: although the green belt encircling London covers an enormous area (some 514,000 hectares), only about 13% of it is public parkland or land accessible for recreation. The vast majority is in private hands – often farmland, utility land, or unused scrub – meaning most Londoners can’t actually set foot on it. Khan provocatively calls some of it “grey belt” rather than green: derelict or low-grade lands that happen to lie within the green belt boundary.
Not everyone agrees with this characterisation. Green belt defenders point out that even if some green belt sites lack scenic beauty, they still fulfil the original mission of checking sprawl and giving breathing room to the city. Environmental groups note that “green” value shouldn’t be measured only by public access – farmland and wooded areas provide habitat, climate benefits, and food production close to the city.
From a historical perspective, London’s green belt was part of a grand bargain: contain the city’s footprint, but also build new towns and dense estates elsewhere to house the growing population. In recent decades, however, London’s population has surged (up by 2 million since 1990) without corresponding new towns or sufficient urban homebuilding, putting extreme pressure on housing costs. Critics say the green belt now inadvertently pushes growth into a “leapfrog” pattern – development jumps over the green belt into far-flung commuter towns beyond, leading to longer commutes and more car travel.
Green Space in South West London: A Case Study in Protected Land
London’s south-west quadrant – encompassing areas like Putney, Wimbledon, Richmond, and Kingston – illustrates the patchwork of protected green sites that exist within the capital. Much of this area is blessed with parks, commons and riverside meadows that are fiercely loved by local communities.
One of the largest open spaces in SW London is Wimbledon Common and Putney Heath, which together form an expansive green oasis straddling the boroughs of Wandsworth and Merton. Covering about 460 hectares of woodland, heath and grassland, these commons have been protected by statute since the 19th century. Further west lies the vast Richmond Park, London’s largest royal park at about 950 hectares, which holds National Nature Reserve status. It serves as a green lung not just for SW London but the whole city, with wild deer herds roaming just 8 miles from Trafalgar Square.
Smaller pockets of protected land dot the area as well. Barnes Common, Wandsworth Common, and Wimbledon Park are all designated as Metropolitan Open Land and protected from development. The cumulative effect is that South West London retains a chain of green spaces running through it – from the vast commons and parks down to smaller gardens and allotments – which give the area a leafier character compared to some other parts of London.
Battles Over Building on Protected Land: The Wimbledon Park Saga
One emblematic clash is the ongoing Wimbledon Park saga, which centers on Metropolitan Open Land at the boundary of Wandsworth and Merton. The All England Lawn Tennis Club (AELTC), world-famous home of the Wimbledon Championships, has been pursuing a massive expansion plan onto land that was formerly the Wimbledon Park Golf Course – land that is part of the historic Wimbledon Park and designated MOL.
The AELTC’s proposal includes 39 new grass courts, an 8,000-seat semi-sunken stadium known as the Parkland Show Court, and a range of other buildings and infrastructure across the old golf course. The site is Metropolitan Open Land and part of a Grade II listed historic park – a landscape originally designed by Capability Brown in the 18th century.
When the plans became public, local residents formed the Save Wimbledon Park campaign, mobilizing around concerns that echo many green belt debates: loss of mature trees, privatization of green space, environmental damage, and breach of public trust. Despite the outcry, the project gained initial approvals from Merton Council and the Greater London Authority. However, the Save Wimbledon Park group swiftly filed for a judicial review, and as of May 2025 a High Court hearing has been set for 8-9 July 2025.
This case illustrates how contentious building on protected land can be, even when that land isn’t fully public. It pits local conservation values against city-level or national interests. It’s also a test case for how flexibly Metropolitan Open Land policy can be interpreted. If the challenge fails and the development proceeds, some fear it could set a precedent emboldening other encroachments on protected land.
London’s Housing Crisis by the Numbers: How Bad Is It?
Behind the push to build on even a sliver of green belt lies a grim and growing housing crisis in London. A few statistics starkly illustrate the challenge:
- Housing Supply Gap: London needs to be adding 80,000–100,000 homes per year to catch up with demand. Yet over the past decade, actual delivery has averaged around 30-40,000 annually.
- Skyrocketing Prices: As of early 2025, the average house price in London is around £556,000 (roughly $700,000) – double the UK average. Even with a recent cooling in the market, prices remain out of reach for most residents.
- Unaffordable Rents: The median monthly rent for a private flat in London now hovers around £1,625. By comparison, the UK median rent is ~£905. Housing charity data shows 1 in 4 Londoners are in poverty after accounting for housing costs.
- Overcrowding and Homelessness: Over 11% of London households are overcrowded, nearly triple the national rate. Khan cited over 90,000 children in London who are officially homeless or in unstable temporary housing.
- Exodus of Key Workers and Youth: High housing costs are cited as a major reason people are leaving London. Employers, from the NHS to tech firms, struggle to recruit and retain staff because workers cannot find affordable housing near jobs.
In short, London’s housing crisis is a multi-faceted problem: too few homes, exorbitant costs, and thousands of people in dire situations as a result. Khan’s decision to countenance building on the green belt must be seen in this context: traditional solutions have fallen short, and the crisis has persisted to the point that previously unthinkable options are now on the table.
Is Building on the Green Belt the Best Solution?
So, is unlocking some green belt land for development the best way to alleviate London’s housing crisis? It’s a question with strong arguments on both sides.
The Case For Building on (Parts of) the Green Belt:
Proponents argue that, given extraordinary housing need, nothing should be off-limits – especially not land that could be put to better use than it is currently. The green belt occupies a huge area around London, and even a small portion of it could yield a significant number of homes. If even 5% of London’s green belt were developed with housing at suburban densities, it might accommodate on the order of 200,000+ homes.
Some advocates focus on “low-hanging fruit”: parcels near existing infrastructure that are visually unremarkable. Another benefit cited is that it may be easier to build family homes with gardens – something London desperately needs – on available land at the fringes, rather than only building high-rise flats on infill sites.
Crucially, supporters claim this doesn’t mean paving over parks or treasured landscapes. The Mayor promises stringent conditions: any green belt release must maximise affordable housing and create net gains in green amenities – so new developments would have to include things like new parks, tree planting, and biodiversity improvements for local residents.
The Case Against (or Risks of) Green Belt Development:
Opponents counter that while green belt building might seem a quick fix, it’s not the optimal solution. First, there is the political and legal quagmire. Widespread green belt development would face resistance, delaying any housing from actually being delivered. There’s also skepticism about whether developers truly need green belt land, or simply prefer it. London currently has hundreds of thousands of unbuilt housing permissions – some critics say before touching the green belt, authorities should force the pace on these already-approved sites.
Another issue is infrastructure cost. Building a new suburb on the outskirts means investing in new transport links, schools, and utilities. This can be very expensive, and historically the government has struggled to fund such infrastructure at scale.
Effectiveness is another question: will releasing green belt land actually result in affordable housing? Some fear it would mostly produce expensive executive homes in commutable villages, because those are the most profitable to build.
Then there’s the point that not all green belt sites are equal. The Mayor says he’ll target “low-quality” land near transport, but deciding what qualifies will be contentious. Building on green belt permanently seals it under concrete. In an era of climate concern, once green belt land is built on, it’s lost as permeable land that can soak up rainwater or grow food near the city.
Alternative Solutions:
Several alternatives to green belt development have been proposed:
- Intensification of existing urban areas: There is still substantial scope to densify parts of London without touching protected land, particularly in outer boroughs.
- Brownfield Redevelopment: London has large amounts of brownfield land that could be turned into housing. Some estimates claim at least 350,000 homes’ worth of brownfield capacity in London.
- Public Housing and Estate Renewal: Many post-war estates have the capacity to densify, adding significant housing without needing new land.
- Incentivising faster build-out of approved projects: If London could somehow get those 300k+ unbuilt permitted homes constructed, that would be a game changer.
- Develop new towns beyond the green belt: One alternative to building through the green belt is to build beyond it – in effect, leapfrog to a new generation of planned towns further out, but with high-speed transport links.
A balanced approach is often suggested: continue maximising brownfield and densification (where communities accept it), and selectively use some green belt land especially where it can create sustainable new communities.
Green Belts Elsewhere: London’s Approach vs Other Cities
London is not the only city grappling with how to manage growth and green space. A look at other UK and international cities shows a spectrum of approaches—with notably different outcomes for housing affordability.
Many British cities have green belts and are facing the same housing supply crunch. Oxford and Cambridge, small cities encircled by green belts, have seen some of the UK’s highest house price inflation. According to the Office for National Statistics, Oxford’s average house price reached approximately £429,000 in late 2023—nearly 12 times the average local salary. Recently, under government pressure, some Oxfordshire districts agreed to remove small sections of the green belt for new housing. Cambridge did release a portion of its green belt north-west of the city to create a new residential quarter (the Eddington development) for university staff and market housing, adding approximately 3,000 homes.
Greater Manchester’s experiment takes a different approach. The region has spent years drawing up a plan that proposes building on some green belt—about 1,900 hectares to deliver 50,000 homes—while protecting the rest. This plan, fiercely opposed in some suburban and rural communities, was revised multiple times to remove the most controversial green belt sites. According to the Greater Manchester Spatial Framework, the region has struggled to meet its housing targets, contributing to significant price increases over the past decade.
International comparisons
Internationally, the contrast becomes even starker. Portland, Oregon uses an urban growth boundary which is reviewed periodically—the city can expand it if needed, but must do so in a planned manner. According to the Portland Housing Bureau, the city has seen housing costs rise significantly, with median home prices increasing approximately 40% between 2015-2023.
In contrast, Tokyo—a city with no green belt but intensive development rights—tells a different story. Research published in the Journal of Housing Economics shows Tokyo builds approximately 100,000 new homes annually in its metropolitan area (significantly more than London delivers despite comparable population), resulting in remarkable price stability. Despite its massive population, Tokyo’s housing costs have remained relatively stable—average condo prices increased minimally during periods when London’s rose substantially. This stability is largely attributed to Japan’s more flexible zoning laws that prioritize the right to build.
Seoul, South Korea provides a fascinating case of a city that had a strict green belt and then partially rolled it back. In the 2000s, the South Korean government decided to relax Seoul’s green belt in targeted areas to release land for development. According to research from the Korea Research Institute for Human Settlements, this policy change contributed to increased housing supply. The government’s 2020s housing plans included lifting green belt restrictions to supply an additional 80,000 homes in Seoul.
London’s current exploration of green belt development aligns with a broader re-thinking in many places: how to balance preserving green space with providing homes. The experiences from these various cities suggest a relationship between housing supply and affordability. Tokyo’s high construction rates—enabled by flexible zoning rather than rigid growth boundaries—have delivered notable price stability. Seoul’s partial green belt reform helped moderate previously rapid price growth. Meanwhile, UK cities with strict green belts consistently struggle with housing affordability.
If London does proceed with building on some green belt land, doing so strategically—focusing on sustainable, transit-linked communities and truly affordable housing—will be key to its success. The coming months of consultation and debate will show whether Londoners are willing to embrace this multifaceted solution. The housing outcomes from cities worldwide suggest that maintaining the status quo is likely to perpetuate the affordability crisis.
Sources:
Khan’s announcement and reactions – Guardian, 9 May 2025 ; Evening Standard; City Hall press info.
Green Belt/MOL definitions – GiGL London environmental data; Wikipedia (Metropolitan Open Land) ; Abercrombie 1944 Plan and 1955 policy .
“Is it green?” debate – Evening Standard (Khan quotes) ; CPRE London (brownfield capacity and green belt value) .
SW London sites – Wimbledon & Putney Commons website and data; Royal Parks data ; Barnes Common LNR info ; Wandsworth Council docs.
Housing crisis stats – Khan speech (90k children homeless) ; UK Parliament report (164k children, temp accommodation spending) ; ONS house price data; Centre for London (overcrowding 11%) ; Centre for Cities (Tokyo vs London housing output, rents) .
Other cities – CPRE Oxfordshire, local plan docs; Greater Manchester Places for Everyone draft; News on Seoul green belt (Korea JoongAng Daily); Centre for Cities on Tokyo.
