Clarification needed on compatibility between multiple planning permissions

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Clarification needed on compatibility between multiple planning permissions

Published 22 marzo 2021

Case Law Update: Hillside Parks Ltd v Snowdonia National Park Authority [2020] EWCA Civ 1440

In this case of a site the subject of multiple planning permissions, the Court of Appeal has given developers pause for thought before embarking on Section 73 or what are known as ‘drop-in’ applications. Although not part of the court’s ruling on the facts of this case, the judgment pondered serious questions about the implications of what many in the industry have come to regard as standard practice as part of re-planning and optimising existing schemes – could a subsequent permission in respect of whole or part inadvertently render an existing consent unlawful or vice versa?

The gravity of those consequences will hopefully cause the Government to issue practice guidance, as the position should not be left to the courts. Further clarification is therefore urgently needed on this concept of compatibility of multiple planning permissions.

This article takes a closer look at the implications of Hillside and how to adopt a cautious approach.


In 1967 permission was granted for 401 houses in Aberdyfi, Mid Wales, including the agreement of a masterplan. That permission had not been fully built out. Between the original grant of permission and 2011 there were 16 successful applications on the same site, each built out in full which meant departures from the masterplan.

In 2017 the Local Planning Authority stated that the 1967 planning permission could no longer be implemented in full because the development carried out in accordance with the later permissions rendered the original scheme impossible to implement. The original permission could not be fully completed in accordance with its masterplan.

This was supported by the judgment of the High Court and Court of Appeal. The Court of Appeal stressed that it is possible for a later planning permission to be carried out without interfering with the work of another over the same land – but on the facts in Hillside it found that there had been such interference. The court referred to the need for a ‘holistic’ approach to be taken to ensure the permission be construed as the sum of its parts and it endorsed the principle that should subsequent permission(s) constitute development that is contrary to the original/earlier permission(s) it would render the entire permission unlawful.

Unfortunately the court did not have to opine on the full implications of that incompatibility, in terms of enforcement against unlawful development – but did indicate that the law should not be left open to what is a matter of discretion. The issue now calls for definitive national guidance on whether the whole of the development becomes unlawful or only development pursuant to the later contradictory permission.

Significance of the decision

The principle of applying for subsequent permissions without jeopardising the ability to carry out the original scheme is routinely used in section 73 applications to amend a condition or drop-in applications (i.e. an application seeking permission on part of a site for a scheme that is different to the scheme on the same part of an earlier permission).

The decision in Hillside does not remove the need or use of such applications but it raises a caution that advice should be sought prior to a Section 73 or drop-in application to ensure the scheme will not fall foul of incompatibility and therefore potentially unlawful development.

What must we look for:

  • Inconsistency; and
  • Interdependency

Inconsistency between the first and second application must be identified at an early stage. In order for the second application to be approved and not invalidate the original permission there must be no physical inconsistencies. For example, the location of houses and additional infrastructure or green spaces must remain in the same locations. Secondly, each application must be capable of being developed completely separately from the other with no interdependencies, shared facilities or cross-cutting conditions.

An option may be to separate the development into two distinct parts with separate conditions, not overlapping. It may also be necessary to amend the existing section 106 agreement to remove or amend obligations which will then be applied to the later permission. Each application should include a statement contemplating the other, acknowledging their relationship and highlighting how consistency and interdependence are achieved. That symbiosis is the key to steering clear of the caveats of Hillside.


Andrew Morgan

Andrew Morgan

London - Walbrook

+44 (0)20 7894 6193

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