Aysen Dennis, R (on the application of) v London Borough of Southwark

A planning permission for a large, integrated development is not severable merely because it provides for phasing, reserves details for later approval, or permits development below stated maxima. Severability in the context of the Pilkington principle requires a clear indication that the permission creates separate, freestanding permissions. A phased outline permission remains capable of engaging the physical-impossibility principle. An amendment which changes an integrated permission into a severable permission enlarges the bundle of rights granted and is material under section 96A of the Town and Country Planning Act 1990.

Southwark granted Notting Hill Genesis an outline planning permission for the phased redevelopment of the Aylesbury Estate. The permission authorised an integrated mixed-use scheme and incorporated parameter plans, a phasing plan and design documents.

In anticipation of a possible detailed “drop-in” permission for phase 2B, Southwark amended the outline permission under section 96A of the Town and Country Planning Act 1990 by inserting the word “severable” into the development description. A local resident challenged that decision, arguing that the original permission was a single, non-severable consent and that the amendment materially enlarged the rights conferred. The central issue was whether the original permission was already severable as a matter of construction.

1. The claim succeeded. Southwark’s decision of 28 March 2023 was ultra vires section 96A and was quashed.
2. A planning permission must be construed objectively as a whole. The court considers the grant, incorporated documents, conditions, reasons, statutory context, ordinary meaning and common sense. The conditions may help define the scope of the authorisation even where they are not themselves operative to grant permission.
3. Under Pilkington and Hillside, physical impossibility is assessed by reference to the whole site covered by the unimplemented permission. Mere inconsistency between permissions is insufficient. The relevant question is whether what has been done under one permission makes it physically impossible to carry out development authorised by the other.
4. Severability in this context means disaggregation into separate, freestanding permissions. Phasing, spatially discrete development areas, reserved matters, flexibility in an outline permission and maximum quantities do not, without more, amount to a clear contrary indication. The same principle applies to detailed and outline permissions.
5. The outline permission required delivery of the phases in the sequence shown in the incorporated Design and Access Statement, with phases 2B and 2C preceding phases 3 and 4. Those arrangements were inconsistent with severance, or at least wholly consistent with a single integrated permission. The permission was therefore not severable before the amendment.
6. By making the permission severable, the amendment would disapply the Pilkington principle in relation to material departures and significantly enlarge the bundle of rights conferred. It was consequently a material change which section 96A did not authorise. The judge also expressed strong reservations about the legality of inserting the bare and uncertain term “severable” without specifying its extent.