Green belt in the outer London boroughs

Green belt in the outer London boroughs works exactly as it does in the shire counties, with one addition that catches people out: London has a second designation, Metropolitan Open Land, which carries the same protection and sits inside the built-up area. A site in Bromley, Havering, Hillingdon or Enfield may be Metropolitan Green Belt. A site in a far more urban setting may be Metropolitan Open Land. In both cases inappropriate development is by definition harmful and should be refused unless very special circumstances exist.

The policy framework is therefore layered. National Green Belt policy in the Framework sets the test, the London Plan adds its own protective policies, and the borough's local plan and its policies map tell you which designation applies to the land in front of you.

Where the Metropolitan Green Belt sits inside London

The Metropolitan Green Belt was drawn around the conurbation and runs through the outer boroughs before extending into Hertfordshire, Essex, Kent, Surrey and Buckinghamshire. Within Greater London the designated land is concentrated in the outer eastern, northern and southern boroughs, and some outer boroughs contain very large tracts of it.

Do not take the designation from a general map. Check the borough's adopted policies map and the national planning data service, which publishes designation boundaries as spatial data. Boundaries follow field edges, railway lines and garden boundaries, and a plot can be split so that the house is outside the belt and the garden inside it.

That split matters. Where the dwelling is excluded and the rear garden is designated, an outbuilding or a garden annexe at the bottom of the plot falls to be assessed against Green Belt policy while an extension on the back of the house does not.

Metropolitan Open Land does the same job inside the built-up area

Metropolitan Open Land is a London designation with no counterpart elsewhere in England. It protects strategically important open space within the built-up area, and the London Plan affords it the same protection as Green Belt, which means the same test of inappropriateness and the same requirement for very special circumstances.

It catches large parks, playing fields, cemeteries, reservoirs, allotments and institutional grounds, often in boroughs nobody associates with Green Belt policy at all. A school playing field in an inner borough can be Metropolitan Open Land, and a proposal for a new sports hall on it is assessed against the same framework as a barn conversion in rural Havering.

So the first question on any London open-land site is which of the two designations applies, because the policy consequence is almost identical and the evidence required is the same. The parallel is the protection given to industrial land, where a designation rather than a site's physical character drives the outcome, as set out in the note on industrial land and no net loss in London.

The five purposes and the test of inappropriateness

National policy states that the fundamental aim of Green Belt policy is to prevent urban sprawl by keeping land permanently open, and that the essential characteristics of Green Belts are their openness and permanence. It then sets out five purposes: checking unrestricted sprawl, preventing neighbouring towns merging, safeguarding the countryside from encroachment, preserving the setting and special character of historic towns, and assisting urban regeneration by encouraging the recycling of derelict and other urban land.

Inappropriate development is harmful to the Green Belt by definition and should be refused except in very special circumstances. The Framework then lists the categories of development that are not inappropriate, subject to conditions, and those categories are the first place to look on any proposal.

Read the current edition of the Framework rather than an older copy. The chapters were renumbered in December 2024, which also introduced the grey belt concept and the associated requirements for major development coming forward on released land, and the Framework was reorganised again by policy code in the edition published on 17 August 2026. Verify the wording and the policy reference before you cite it.

Householder extensions and replacement dwellings

This is the bulk of Green Belt casework in an outer London borough, and two phrases decide it.

"Disproportionate additions over and above the size of the original building" uses the original building as the baseline, meaning the dwelling as it stood on 1 July 1948 or as built if later. Previous extensions count against you. A 1960s house that has already been extended twice has very little headroom left, and the calculation has to start from the original volume rather than from what is there today.

"Not materially larger" applies to replacement dwellings and is a stricter test than it sounds. A replacement that is the same floor area but twice the volume, because the roof has become a full second storey, is materially larger.

Many boroughs publish a yardstick in supplementary guidance, expressed as a percentage increase in volume or floor area over the original. The figure varies between authorities and it is guidance rather than policy, so check the borough's own document and treat the percentage as a starting point for a judgement rather than an entitlement. Submit the calculation as a table: original volume, existing volume, proposed volume, percentage increase, with the method stated.

Previously developed land and the openness question

Redevelopment of previously developed land in the Green Belt is not inappropriate where it would not have a greater impact on the openness of the Green Belt than the existing development. That is a comparison, and it has to be evidenced.

Openness is assessed spatially and visually. The spatial element is about volume, footprint and spread: how much built form occupies the land and how it is distributed. The visual element is about how the development reads from public vantage points, including whether it is seen against a backdrop or in open country.

So a scheme that reduces footprint while increasing height may be better spatially and worse visually, and the assessment has to address both. Activity counts too. Replacing a disused depot with housing may reduce built volume while introducing parking, lighting, fencing and domestic paraphernalia across a wider area, and an inspector will weigh that.

Prepare a comparison table of footprint, volume, height and developed area, with a plan showing the existing and proposed developed extents hatched. Drawings win these cases more often than text does. The design-led approach boroughs use to establish capacity elsewhere is a useful discipline here as well, as described in the note on optimising site capacity through a design-led approach.

Limited infilling in villages

Several outer London boroughs contain settlements within the Green Belt that function as villages, and the infilling exception can apply to them. Two questions follow.

Whether the settlement is a village is a matter of fact assessed on the ground, looking at its size, the range of services it contains, its historic identity and whether it reads as a settlement rather than as a ribbon of houses. Some boroughs identify villages in the local plan, which settles it. Where the plan is silent, the argument has to be made.

Whether the proposal is limited infilling turns on the gap. A single plot between two existing dwellings in a built-up frontage is the classic case. A paddock at the edge of the settlement, or a scheme of six houses on a single frontage gap, generally is not. The exception does not extend to building on the edge of a village and calling it infill.

Very special circumstances and what a borough expects to see

Where the proposal is inappropriate, the only route is very special circumstances. The balance is structured: identify the harm by reason of inappropriateness, which attracts substantial weight, add any other harm such as landscape, heritage or highway effects, and weigh the total against the other considerations advanced in favour.

The considerations that have carried weight in practice tend to be specific and quantified rather than general. Delivery of affordable housing against an identified need. A public benefit that can only be delivered on that land. The removal of existing harm, such as the clearance of a derelict and visually damaging site. Very special circumstances rarely consist of a single factor, and they are never simply that the development would be useful.

Expect the borough to want a Green Belt assessment inside the planning statement, a landscape and visual appraisal where the site is prominent, volume and footprint comparisons, and a clearly structured very special circumstances case with each limb evidenced. Where growth is being directed to designated locations instead, that context is worth understanding, and it is covered in the note on what a London allocation changes.

Enter your postcode on PlanScope to see which supporting documents a Green Belt or Metropolitan Open Land site is likely to need.

This is general guidance, not legal advice. Designations, local yardsticks and policy wording differ between boroughs and editions, so check the adopted policies map, the borough's guidance and the current Framework before relying on anything here. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.