The housing delivery gap inside the NPPF's Green Belt numbers
Nic Cuff
The Draft London Plan's own viability evidence shows current development values cannot support NPPF and plan policy requirements, putting a meaningful share of its headline housing number in doubt.
The Draft London Plan, published on 16 July 2026, targets 558,451 new homes over the next decade. Around 56,000 of them, roughly one in ten, are expected to come from Green Belt release across outer London boroughs including Barking and Dagenham, Barnet, Croydon, Enfield, Havering, Hillingdon and Redbridge.
The plan's own viability evidence casts doubt on whether that share is deliverable.
The methodology behind the numbers uses a benchmark land value, or BLV, to work out what a viable scheme looks like. Most site types get a 20% premium above existing use value. Green Belt agricultural land gets nil premium, valued at roughly £37,000 per hectare, about £15,000 per acre.
Apply that to a real example: a 14-hectare Green Belt site earmarked for 1,438 homes. The total benchmark land value comes to just £518,000. Divided across the homes planned, that works out to about £360 per home plot. For comparison, industrial land in outer London is valued at roughly 219 times higher under the same methodology.
The underlying viability study does not dress this up as good news. It flags two specific problems. First, the residual land value uplifts the plan relies on depend on public subsidy rather than market-led development actually happening. Second, even at nil benchmark land value, current day one residential development values alone cannot viably support NPPF and Draft London Plan policy requirements in lower-value areas.
No rational landowner accepts a nil premium voluntarily. The alternative, compulsory purchase, takes five years minimum before a spade goes in the ground. Meanwhile the politics are already turning against release: Croydon's council leader opposes Green Belt release outright, and Reform has taken control of Havering's administration.
The study is blunter still on the lowest-value areas. In Value Band F, no viable delivery scenario exists, even with grant funding layered in.
None of this means the 558,451 figure is fiction. It means the routes to it are narrower than the headline suggests, and the Green Belt component in particular rests on land economics that the plan's own evidence says do not currently work. Read as a delivery mechanism, the numbers do not stack up. Read as an aspirational trajectory, they might survive contact with reality, but only if subsidy, compulsory purchase timelines and local political resistance all break in the plan's favour at once.