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Overlapping Permissions – Caselaw Update Post Hillside

Property planning overlapping permissions

Following the Supreme Court decision in Hillside Parks Ltd v Snowdonia National Park Authority (Hillside) in 2022 which considered the effect in planning terms of implementing two or more inconsistent planning permissions on the same site (a situation commonly arising with drop-in permissions), we now have (as expected) further judicial guidance on some of the principles established in Hillside. The latest caselaw comprises a High Court decision from Holgate J in R (Dennis) v London Borough of Southwark and a Court of Appeal decision R (Fiske) v Test Valley Borough Council.

The statutory planning code does not deal with the effect of implementing two or more inconsistent planning permissions on the same site. This lacuna in the law has instead been filled by way of evolving caselaw, which by its nature, continues to create uncertainty in the application of these principles to each project and the relevant permissions.

In December 2023, the Court of Appeal held in R (Fiske) v Test Valley Borough Council that when deciding a planning application which was incompatible with an earlier planning permission for the same site, a planning authority was not required (in law) to take account of that incompatibility as a material consideration in deciding the later application. More recently, the Planning Court decision from Holgate J in R (Dennis) v London Borough of Southwark has provided judicial guidance on the concept of “severability” identified by the Supreme Court in Hillside.

Following Dennis, the current position in law on overlapping inconsistent permissions (whether detailed or outline) can be summarised as follows:

  • Pilkington v Secretary of State for the Environment [1973] 1 WLR 1527 is still good law and where this situation arises, the starting point is to consider whether building out both permissions results in physical impossibility as between the two developments;
  • If physical impossibility arises which cannot be overcome between the overlapping permissions, the effect would be to make unlawful any further development of the underlying permission and to keep both permissions alive whilst continuing to build out, one must look to Hillside to identify if the exceptions in that case apply
  • Those Hillside exceptions comprise (i) whether the underlying permission is a “severable” permission or (ii) whether the difference between them is a “mere inconsistency”. If either exception applies this overcomes the effect of Pilkington and both permissions may be built out
  • The decision in Dennis now provides further judicial guidance on the meaning of “severability” – a severable permission is one that amounts to a collection of separate, discrete or freestanding permissions – but in each case it will depend on the construction of the relevant planning permission. The effect of this may well be to make it harder to establish severability – and the implications of a severable permission also need careful thought.  The inclusion of a phasing condition will not in and of itself automatically mean the permission is severable.

It is worth noting that:-

  • Despite the fact that both Pilkington and Hillside were full permissions in Dennis, Holgate J considered that Pilkington could apply to outline permissions although he acknowledged that outline permissions with all matters reserved provide a great deal of flexibility in terms of the detail that may come forward and that this flexibility in practise could defer to a much later point when (if at all) Pilkington was engaged.  Indeed, whether physical impossibility arises at all may also be less likely for outline permissions.
  • The scope of the Hillside exception in terms of “mere inconsistency” was not explored but Holgate J noted again that in Hillside the Supreme Court said that the Pilkington principle should not be pressed too far, in particular to inconsistencies in relation to large scale multi-unit developments.

It remains important that when looking at the effect of implementing two inconsistent planning permissions (whether detailed or outline) careful attention must be given as to whether physical impossibility arises applying Pilkington, and if so, how the exceptions in Hillside might apply to reduce the risk that further development pursuant to the underlying permission might be made unlawful if a subsequent permission or drop-in is implemented. That assessment must have regard to the fact that the law on this subject is uncertain and, through continuing caselaw, is very likely to evolve further.

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