In a recent decision of the High Court in R (Aysen Dennis) v London Borough of Southwark, Holgate J held that an outline planning permission for a large-scale mixed use regeneration project in South London could not be regarded as “severable” so as to allow a developer to carry out one phase of the development under a separate “drop-in” permission.

The developer had obtained outline planning permission in 2015 for the regeneration of the Aylesbury Estate in Southwark. Following the grant of the permission, the Council’s Local Plan adopted policies increasing the requirement for new homes and affordable housing. To meet these new requirements the developer needed to exceed the parameters for development (including height of buildings) approved under the outline permission. They obtained a separate “drop-in” permission to allow this but wanted to build out the rest of the development under the outline planning permission.

Under the so-called rule in Pilkington (recently approved, with tweaks, by the Supreme Court in the Hillside case), if it is not physically possible to carry out development under an unimplemented permission, having regard to what has been carried out under another permission on the same land, then the unimplemented permission cannot lawfully be built out.

The Supreme Court in Hillside had said that the Pilkington rule could be disapplied where the permission in question was “severable”: in other words, where the permission could be disaggregated into a series of mini-permissions. But the Supreme Court also said that unless it was explicit that a planning permission were severable then it should be assumed a single permission had been granted in the absence of clear indications to the contrary.

In Dennis, the developer had applied for a non-material amendment to the outline permission (under section 96A Town and Country Planning Act 1990) to add the word “severable” to the operative part of the permission, so it would then read as a permission for a “severable phased development”. The intention was not to make the outline permission severable by virtue of the non-material amendment but to formalise the existing severable nature of the outline permission.

Following the Hillside decision, several practitioners had suggested it might be possible to use section 96A amendments to existing permissions as a way of securing their severable nature. It was not argued in Dennis that the section 96A amendment had this effect and Holgate J made clear that any such argument would have failed as the effect would have been material and so outside of the scope of section 96A (which only deals with non-material amendments).

The argument in Dennis instead concerned whether the underlying un-amended outline permission was severable. Holgate J held that it was not. He rejected the arguments that because the permission was outline (whereas in Pilkington and Hillside the permissions were full) and was for “phased” development (again different from Pilkington and Hillside) that this was enough to make clear the severable nature of the outline permission.

Instead, he placed weight on the following:

  • Planning permission had been granted for a  multi-unit development as an “integrated whole”. He said, “in deciding whether to grant permission the local planning authority will generally have had to consider a range of factors relevant to the proposal taken as a whole”.
  • The Planning Statement, Design Code Strategy and other supporting documents were incorporated under the planning permission and these repeatedly emphasised the integrated nature of the “comprehensive regeneration” project with “connected neighbourhoods” and a “degree of continuity and consistency across the Estate”.
  • The incorporation of parameter plans was also regarded as an important indicator of a single individual permission, and was the requirement for delivery of implemented phases.

Holgate J concluded that there were no “clear indications” that the permission was severable and, in fact, the above factors suggested the opposite. He also noted (though this is not relevant to this decision) that there mere addition of the word “severable” by way of the section 96A application was too uncertain to render the permission severable. This word on its own did not identify which elements of the development were severable. In other words, it was unclear if the permission could be disaggregated on a phase by phase only basis or whether individual units also benefited from the suggested severability.

The case is the first authoritative application of the Supreme Court’s ruling in Hillside and has significant implications for the lawfulness of drop-in permissions, especially for permissions granted before Hillside where it was often (wrongly) assumed that phased developments could be severed to allow the use of “ drop-in” permissions.

Great care will now need to be taken when preparing applications for large-scale developments to make sure that severability is incorporated into the operative part of the permission at the time of the original grant and is reflected in the supporting documents, and that severability is detailed by reference to each phase or sub-phase (as required). In our view, it would also be preferable for the permission to distinguish on its face the conditions applicable to each severable phase (or sub-phase).


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