Why data centres end up in the Green Belt
Data centres need large, flat sites close to power, fibre and existing clusters, and around London and the other major cities much of that land is Green Belt. The M25 corridor, the Slough and Heathrow area and Hertfordshire have seen a run of large proposals, several decided by the Secretary of State.
National policy now actively supports the sector. Policy E1 of the National Planning Policy Framework (August 2026) expects plans to provide for data centres, their generating capacity and the grid connections they need. But there is no data centre exception in Green Belt policy, so each scheme still has to fit the Green Belt tests.
The two routes: grey belt or very special circumstances
Under NPPF Policy GB6, development in the Green Belt is inappropriate unless it falls within one of the categories in Policy GB7, and inappropriate development should not be approved except in very special circumstances. For data centres, the realistic routes are:
- Grey belt (Policy GB7(g))Development on grey belt land is not inappropriate if it would not fundamentally undermine the purposes of the remaining Green Belt across the plan area, there is an evidenced unmet need for the type of development, and the site is in a sustainable location. If it passes, no very special circumstances case is needed.
- Very special circumstances (Policy GB6)If the land is not grey belt, the harm to the Green Belt, which carries substantial weight, and any other harm must be clearly outweighed by other considerations, such as national need, the lack of alternative sites and economic benefits.
What counts as grey belt
Grey belt is Green Belt land made up of previously developed land and/or other land that does not strongly contribute to three of the Green Belt purposes in Policy GB2: checking the unrestricted sprawl of large built-up areas, preventing neighbouring towns merging, and preserving the setting and special character of historic towns. The assessment is site-specific, and the council's own Green Belt review is a starting point, not the final word. In the Abbots Langley appeal, grey belt status was decided through the application itself, rather than waiting for the council's own assessment.
Recent decisions
- Abbots Langley, Three Rivers (May 2025)A hyperscale data centre and country park off Bedmond Road, refused by Three Rivers District Council, was allowed on behalf of the Secretary of State. The site was found to be grey belt, and significant weight was given to the need for capacity, with the scheme meeting around a third of the need in the Hemel Hempstead availability zone, and to the lack of alternative sites.
- Woodlands Park, Iver (July 2025)The Secretary of State approved a large data centre on a former landfill site, finding it to be grey belt. In January 2026, facing a judicial review, the Government accepted that it had been wrong to decide that no Environmental Impact Assessment was needed and agreed that the permission should be quashed. The lesson is that procedure matters as much as policy.
- Manor Farm, Slough (June 2026)The Government approved a data centre of up to 147MW at Manor Farm after a public inquiry. The developer argued that the part-previously developed site was grey belt, while Slough Borough Council pointed to alternative sites on the Slough Trading Estate. The case shows how need and alternatives are tested.
Building the case
- Evidence the needGB7(g) requires an evidenced unmet need for the type of development. That means market and capacity evidence, the availability zone the site serves, and why the need cannot be met elsewhere. Policy E2 also asks decision makers to consider locational requirements such as grid access and co-location with power generation.
- Show the site is grey beltA purpose-by-purpose assessment against GB2 (a), (b) and (d), with landscape evidence on how the scheme would sit in the wider Green Belt.
- Sustainable locationGB7(g) refers to sustainable locations with reference to the transport policies. Staff numbers are low for data centres, but access, construction traffic and travel planning still need a clear answer.
- PowerA credible grid connection, or a strategy for on-site generation, is often what persuades decision makers that the benefits will actually be delivered.
- Environmental evidenceEIA screening done properly, noise from cooling plant and generator testing, air quality, water use and heat reuse. Recovered data centre heat now counts as renewable and low carbon energy in the NPPF.
- Fallback if it is not grey beltPrepare the very special circumstances case in parallel, so the application does not fall if the decision maker disagrees on grey belt.
Local plans are catching up
Councils are now expected to plan for data centres, and London's draft new London Plan, published in 2026, points data centres towards grey belt land. Local plan reviews in places such as Three Rivers, Hertsmere and Hillingdon are opportunities to promote sites before applications. For a wider view of consenting routes, including Nationally Significant Infrastructure Project directions, see our data centre planning service.
Local planning advice
Frequently asked questions
Can a data centre be built in the Green Belt?
Yes, in the right circumstances. If the site is grey belt, there is an evidenced unmet need and the location is sustainable, the development is not inappropriate under NPPF Policy GB7(g). Otherwise it needs very special circumstances under Policy GB6.
What is grey belt land?
Green Belt land that is previously developed and/or does not strongly contribute to checking the sprawl of large built-up areas, preventing towns merging, or preserving the setting of historic towns.
Have any Green Belt data centres been approved?
Yes. A hyperscale data centre at Abbots Langley was allowed in May 2025 on grey belt land, and a scheme of up to 147MW at Manor Farm, Slough, was approved in June 2026. The Government accepted in January 2026 that its approval at Woodlands Park, Iver, was flawed because an EIA should have been required.
Does a data centre need an Environmental Impact Assessment?
Large schemes often do. Screening must be done properly: the Government accepted that its Iver approval was flawed because it wrongly decided no EIA was needed.
This guide is general information for applications in England and is not advice on your specific project. Requirements differ in Wales, Scotland and Northern Ireland, and every council publishes its own local validation list, so always check the detail with your local planning authority.