The Permissive Ten

The companion paper established that London runs more than thirty separate planning systems for small sites, and that where a borough lands on the outcome differential tracks the price of its housing. This first follow-up turns that instrument on the ten boroughs that approve most generously relative to what their caseload should yield, and asks the question the price gradient invites. When a borough says yes more often than expected, is it because its plan says yes, because it has no choice, because of who runs it, or simply because of who is asking?

The answer runs against the intuitive model. Ten superficially identical positive numbers turn out to be produced by at least four different mechanisms, and only one of them is something another borough can decide to adopt.

§1 Why these ten: the boroughs that say yes

The differential measures the gap between the approvals a borough actually grants and the approvals London-average decision behaviour would have produced on that borough's particular caseload, once site type, transport accessibility, conservation status and unit count are controlled for. A positive number means a borough is more generous than its mix predicts. The ten boroughs below are the ten most generous in London, and they span a remarkably narrow band of outcome, from Camden at the foot of the group to Richmond more than twenty points clear, across a remarkably wide band of price.

Bexley at £420,000 and Kensington & Chelsea at £1.1 million sit within four points of each other on outcome and a factor of more than two-and-a-half apart on price. Whatever is producing the shared "yes" cannot be a single thing, because the boroughs producing it have almost nothing in common but the answer. The rest of this essay separates the routes by which a borough arrives at generosity, because the routes are what a reader trying to learn from these boroughs actually needs, and three of the four turn out to be unavailable on request.

§2 What the number hides: permissiveness has a shape too

The move that unlocks these boroughs is to disaggregate the borough number to site type, where uniform restrictiveness means one thing and concentrated restrictiveness another. Applied at the permissive end, the cut returns a different but equally informative pattern. Where the hard boroughs are depressed unevenly, a single typology carrying the borough, the permissive boroughs are lifted almost uniformly. Generosity, unlike restriction, tends to be a general posture rather than a typology-specific policy, which is the first clue that what produces it is rarely a single written rule.

The one row that breaks the pattern is the one that proves it. Camden welcomes conversions at +26 and resists demolish-and-rebuild at −7, and that split is not a quirk of the data: it is written into the plan. Camden's housing policies positively support the subdivision of large houses into self-contained flats and resist their re-amalgamation, while its climate-mitigation policy subjects any substantial demolition to a retention test it is hard to pass in a borough this rich in heritage. The result is a borough that says yes to multiplying units inside an existing envelope and no to knocking the envelope down. Where a plan does the work, the shape shows it. The interest of the other nine boroughs is that their shapes are almost flat, which means the plan is mostly not what is doing the work.

§3 The plans mostly do not say yes

This is the finding that reorganises the essay. The intuitive model (permissive outcomes flow from permissive plans) survives in exactly one of the ten boroughs. Read the adopted development plans of the others and a striking thing happens: several of the most generous boroughs carry small-sites policies that, if anything, ought to suppress approvals.

Kensington & Chelsea's signature housing policy exists to resist the amalgamation of homes, a defensive measure against the super-prime tendency to merge flats into single grand houses, and its design and heritage regime gates almost every site. Westminster's plan encourages small-site delivery in principle but caps new homes at 200 square metres, requires a fifth of the floorspace on even sub-ten-unit schemes to be affordable, and protects existing units against loss; on paper it is one of the more demanding small-sites regimes in London. Hammersmith & Fulham's plan runs standard London-Plan-conformant supply policy and layers heritage protection on top that constrains, rather than enables, the redevelopment of older stock. None of these three reads like a permissive plan. All three over-approve.

And on the other side of the ledger, two of the boroughs whose plans are most demonstrably not permissive sit high in the table for a reason that has nothing to do with generosity. Southwark carries an explicit policy refusing the subdivision of any dwelling under 130 square metres; Haringey carries a presumption against the loss of garden land and a family-housing protection zone. Both restrain small sites in their adopted text. Both nonetheless approve above expectation, because both are absorbing some of the largest small-sites housing targets in London and run an administration disposed to grant and defend the borderline scheme. The plan is a brake; the outcome is generous; the explanation is structural, not textual.

The scatter is the argument in one image. There is a genuine upward slope (wealth and approval move together across London, as the companion paper found), but the cloud is loose, and the most instructive boroughs are the ones that defy it. Bexley sits far above the line: cheap, and yet more permissive than boroughs worth twice as much. Sutton and Ealing sit above it too. These are the boroughs that have found a route to yes that does not run through the price of their housing, and they are, not coincidentally, the boroughs whose route can be copied.

§4 Four ways to say yes

Reading the ten plans against the ten outcomes resolves the single positive number into four distinct mechanisms. The verdicts below assign each borough to the mechanism that best accounts for its generosity; where two operate, the table names the dominant one and the text takes up the nuance.

Permissive by plan. Only Bexley arrives at generosity by the route the intuitive model expects. Its 2023 Local Plan, among the newest in London, states that proposals for new dwellings on small brownfield sites, including infill and backland, "will generally be encouraged", and builds the resulting windfall into its housing trajectory. It approves because it has decided to, and written the decision down where an applicant, an officer and an Inspector can all read it. Camden belongs in this category with an asterisk: its plan plainly drives its outcomes, but it is permissive on one typology and restrictive on another by design, so it is better described as a borough with a precise written posture than a generally permissive one.

Permissive by structure. Ealing, Southwark, Haringey and Sutton are generous because of arithmetic and administration rather than encouragement. Each carries one of London's heavier small-sites obligations (Southwark among the top three boroughs by target, Sutton reliant on small sites for an estimated four-fifths of its housing supply) and each runs a delivery-minded administration inclined to grant and to defend. Two of them, Southwark and Haringey, do this in spite of adopted policies that restrain subdivision and backland, which is the clearest possible demonstration that their generosity is a posture rather than a policy. Sutton's case is the structural one in its purest form: an ageing 2018 plan that loses weight against the small-sites presumption with every passing year, in a borough that cannot meet its numbers any other way. It says yes because it must.

Permissive by wealth. Richmond, Kensington & Chelsea, Hammersmith & Fulham and Westminster are the boroughs whose plans least explain their outcomes, and the explanation that remains, once the plan has been ruled out, is the applicant. This is the mechanism §5 takes up, because it is the one that matters most and travels least.

§5 The wealth mechanism, and why it cannot be copied

The differential is a careful number. It already controls for the things that make one borough's caseload easier than another's: the mix of site types, transport accessibility, conservation coverage, the size of the schemes. What it cannot control for, because the dataset does not record it, is the quality of the application itself: the architect, the planning consultant, the heritage statement, the daylight modelling, the capacity to negotiate a section 106 and to absorb an affordable-housing contribution on a small scheme without the numbers collapsing. In the richest boroughs, the same site arrives in front of an officer as a materially better-prepared proposal, because the applicants can afford to make it so. A plan that gates on design quality is not a permissive plan, but it behaves like one when every applicant clears the design gate.

This is why the four wealthy boroughs over-approve under plans that read as neutral or restrictive. Kensington & Chelsea's amalgamation brake and Westminster's floorspace cap and affordable-housing charge are real, and they bite, but they bite hardest on the marginal, under-resourced application, which is exactly the application that does not arrive in these boroughs. The schemes that do arrive are professionally assembled to pass, and they pass. The differential records the result as generosity. It is more accurately described as a borough whose applicants are wealthy enough to meet a demanding plan on its own terms.

The consequence for any borough trying to learn from these examples is decisive: the wealth mechanism cannot be adopted. A council cannot vote to receive better-prepared applications. It can only change its plan, change its posture, or wait for its plan to age, which is to say it can choose Bexley's route, or Sutton's, or Ealing's, but not Kensington & Chelsea's. The most generous boroughs in London are, for the most part, the least useful as models, because the thing producing their generosity is not in their gift. The useful models are the cheap ones.

§6 The appeal record at the permissive end

The companion essays make the same point from opposite ends, and the finding stands on its own here too: a refusal is, across London, very close to terminal: only about six in every hundred are appealed, and the Inspectorate upholds the borough more often than not. But the overturn rate is not flat across the table. The hardest boroughs are overturned at roughly sixteen per cent of decided appeals; the most permissive, at around twenty-four, with the difference running in the direction that first seems backwards (r = +0.40 between difficulty gap and overturn rate). Permissive boroughs lose more of their appeals (Richmond is overturned at better than a third of decided cases) not because their decisions are worse, but because the refusals that survive in a generous borough are, by definition, the marginal ones. A borough that approves most of what it receives refuses only the schemes it is least sure of, and those are precisely the schemes an Inspector is most likely to wave through.

The reading matters for the verdict in two ways. It confirms that the permissive boroughs are not being propped up by the Inspectorate: their generosity is granted at first instance, by them, not imposed on review. And it cautions against treating the appeal record as a measure of a borough's stance: a high overturn rate at the permissive end means the borough rarely refuses, not that it refuses badly. The appeal corpus describes the texture of a borough's decisions; only the upstream plan establishes the reason behind them.

§7 The spine: Richmond versus Bexley

The two boroughs at the head of the table make the essay's case between them. Richmond and Bexley are separated by close to three points of outcome and a quarter of a million pounds of median price, and they reach almost the same generous answer by routes that could hardly be more different. Bexley says yes in writing, at a London-cheap price, through a 2023 plan that encourages the small-site development its applicants bring forward. Richmond says yes through a fresh plan that adopts the small-sites duty too, but gates it on character and garden protection, in a borough wealthy enough that its applicants clear those gates as a matter of course. Strip the wealth out of Richmond and the character gate would start refusing schemes; strip the wealth out of Bexley and the plan would still say yes, because the plan, not the applicant, is what says it.

For a hard, cheap borough wondering what generosity would cost it (Havering, at the same price as Bexley and twenty points below it on outcome) the instructive neighbour is therefore Bexley, not Richmond. Richmond's example asks a borough to become wealthy, which it cannot do. Bexley's example asks a borough to write an encouraging small-sites policy and mean it, which it can.

§8 Which yeses are durable

Separating the mechanisms also ranks them by durability, which is what a borough (or a developer reading a borough) actually needs to know. Bexley's generosity is the most durable, because it is the most deliberate: it lives in an adopted plan and will outlast any individual administration or applicant. The structural boroughs are contingent. Ealing, Southwark, Haringey and Sutton are generous while their targets are high, their plans are old or permissive-by-omission, and their administrations are willing; change any of the three and the posture can reverse. The point is not hypothetical: Southwark and Haringey both changed political control in May 2026, after the window this data covers, and a permissiveness that rests on administrative disposition is exactly the kind that a change of disposition can withdraw. The wealth boroughs are durable but inimitable: their generosity will persist as long as their applicants are rich, which is indefinitely, but it offers nothing a poorer borough can use.

So the league table of permissiveness, read for lessons rather than for ranking, inverts. The borough at the bottom of the ten (Bexley, cheapest and least celebrated) is the only one whose generosity another borough could choose to reproduce. The boroughs at the top, the famous and expensive ones, are the least useful precisely because their advantage is the one thing a plan cannot legislate.

§9 Conclusion

This first follow-up asked what produces a borough's generosity, and found that ten identical-looking positive numbers are produced by four different mechanisms (a written plan, a structural obligation, an administrative posture, and the wealth of the people applying), only the first of which is available to a borough on request. The differential found the generosity; the type cut showed us that it is broad rather than written; and the plan audit confirmed what that cut already suggested: for most of these boroughs, it is not in the plan at all. The boroughs that say yes are not, in the main, the boroughs with permissive plans. They are the boroughs that can afford to behave as though they had one, and the single exception, which actually has one, is the cheapest of them all, and the only one worth copying.

Sources & confidence

Outcome differentials and type-disaggregated cells: London small-sites planning dataset (LSSPD), build 4 June 2026 (borough_differential.csv, type_differential_cells.csv). Prices: borough median, Land Registry (national_ps2_wealth_gradient.csv); the price–differential correlation across the 31 boroughs with comparable medians is Pearson r ≈ +0.53 (log-price +0.56). Appeal overturn: LSSPD matched-appeal cohort, 458 decided small-site appeals; London overturn 21.0%, permissive boroughs ~24%, r ≈ +0.40 with the difficulty gap. Plan audit: each borough's adopted (and where relevant emerging) Local Plan: Bexley Local Plan (adopted 26 April 2023, Policy DP2); Richmond Local Plan (adopted 7 October 2025, Policy 16); Kensington & Chelsea Local Plan (adopted 24 July 2024, Policies HO1/HO2); Westminster City Plan 2019–2040 (partial review adopted January 2026, Policies 12/13); Hammersmith & Fulham Local Plan (adopted 28 February 2018); Camden Local Plan (adopted 3 July 2017, Policies H3/H7/CC1); Ealing development-plan suite (2012–2013, new plan at examination); Southwark Plan 2022 (adopted 23 February 2022, Policy P3); Haringey DPDs (adopted 24 July 2017, Policies DM7/DM16); Sutton Local Plan 2018.

What this can and cannot tell you. The descriptive claims are firm: these ten boroughs approve above their caseload-expected rate, their generosity is broad across site types, and their adopted plans range from actively encouraging (Bexley) to actively restrictive (Kensington & Chelsea, Westminster). The mechanism attribution is an interpretation, not a measurement: the "wealth" reading is an inference from the residual that survives once plan and structure are accounted for, and it cannot be isolated from unobserved application quality, which is, in fact, the channel it names. Political control is stated for the 2022–2026 data window; the May 2026 elections changed control in several of these boroughs (Westminster, Southwark and Haringey among them), which is itself the point made about the contingency of structural and political permissiveness. Where a borough's emerging plan or a single appeal would sharpen the verdict, the text says so rather than reaching past the record.