An uphill struggle? Drop-in planning permissions and incompatibility following the Hillside case


The recent Court of Appeal case of Hillside Parks Ltd v Snowdonia National Park Authority (2020) is the latest in a series of recent planning law cases including Lambeth v Secretary of State for Housing Communities and Local Government (2019, Supreme Court- inclusion of planning conditions restricting sale of certain goods) and Finney v Welsh Ministers (2019, Court of Appeal – amending description of development) that has been decided against the developer. The Courts seem to be moving towards a simpler but less flexible planning system. This is in contrast to the Government’s recent changes intended to promote flexibility in the planning system.

‘Drop-in’ planning permissions are sometimes used by developers when a discrete part of a development needs to change. A ‘drop-in’ planning permission can authorise a separate development covering the relevant part of the original scheme. Until Hillside, this approach was frequently used because it provided flexibility for developers, but it always required careful consideration of the relevant case law to ensure that the strategy adopted was lawful in the circumstances.  

Following Hillside, the law on ‘drop-in’ planning permissions has changed. On the face of it, it is no longer lawful to ‘drop-in’ a new planning permission into a full unphased planning permission and then continue development under the original permission. Hillside makes it clear that if two developments on the same site are incompatible, once the later permission is built out, no further development can take place pursuant to the earlier permission. This will apply to the whole site, not just the area affected by the ‘drop-in’. Hillside does not address whether the carrying out of a material operation in order to implement a ‘drop-in’ permission will render further development under the original permission unlawful or whether the incompatibility arises at a later point than the act of implementation itself. This is a point for the Courts to consider in the future.

Hillside does not change the law on incompatibility of planning permissions, rather Hillside applies existing principles decided in cases concerning small scale development to a large housing site subject to an approved masterplan.

Where the original development is authorised by a phased outline planning permission, it may still be possible to use a ‘drop-in’ permission to secure changes. The ‘drop-in’ application will need to be accompanied by an application to amend the existing permission to ensure that it can still be lawfully built out. This is because the approved plans for the original development will need to be changed to ‘carve-out’ the area that is subject to the ‘drop-in’. There may also be other circumstances in which a ‘drop-in’ permission can be used, but, following the Hillside case, advice should be sought before including ‘drop-in’ permissions as part of a planning strategy. 

The case of Finney v Welsh Ministers (2019) decided that the description of development in a planning permission can only be amended using non-material amendments (“Section 96A”). This means that a ‘drop-in’ planning permission can only be used in two situations. First, if the description of development in the original planning permission is sufficiently vague so as not to require amendment to accommodate the ‘drop-in’ permission, or second, the amendment to the description of development is sufficiently minor to be consented to under Section 96A. In short, although ‘drop-in’ applications are possible for some schemes, they will become less common.

Whether implementation of a ‘drop-in’ planning permission can render development already carried out pursuant to an existing permission unlawful was not addressed in Hillside. Our strong view is that implementation of a ‘drop-in’ planning permission cannot cause development already lawfully carried out under an existing planning permission to become unlawful. This would be against the key planning principle that a local planning authority cannot bring enforcement action against development that has been lawfully carried out.

Developers can mitigate the impact of Hillside on the flexibility of planning permissions by using more granular phasing in their schemes or by using less detailed descriptions of development. This is easier to achieve on a phased planning permission. Where development is ongoing and a ‘drop-in’ permission is being contemplated, developers need to be aware of the risk that implementation of a ‘drop-in’ permission may prevent further development under the existing planning permission. This could have significant programme and cost implications and may also cause problems at refinancing and disposal of the property.

The two key points for developers to note after Hillside are:

  1. Lawfully constructed development cannot become unlawful due to the implementation of a ‘drop-in’ planning permission.
  2. The use of ‘drop-in’ permissions will be more difficult, and advice should always be sought before using this consenting route.