The recent decision of the Supreme Court in the case of Hillside Parks Ltd v Snowdonia National Park Authority [2022] UKSC 30 has caused a great deal of discussion in planning circles, with the judgment having potentially significant consequences for developers seeking to amend development proposals as sites are brought forward.

Background to the decision

In summary, full planning permission was granted in 1967 for the construction of 401 homes on land which is now located within Snowdonia National Park. Subsequent to the original grant of planning permission, the site owners sought to make changes to the development permitted through a series of further applications which departed from the masterplan approved under the 1967 permission.

By 2017 the site had been acquired by Hillside Parks Ltd, and the planning authority wrote to Hillside advising them that they considered it was now impossible to undertake any further development pursuant to the 1967 permission and asking the developer to stop work on site until the planning position was regularised.

Hillside sought a declaration in the High Court to confirm the fact that the 1967 permission remained valid, and this was subsequently refused, with the judge holding that the physical alterations to the land meant it was physically impossible to complete the development in accordance with the 1967 permission and that further development was therefore unlawful.

The developer appealed, unsuccessfully, to the Court of Appeal and subsequently to the Supreme Court, whose judgment was handed down last week. The Supreme Court refused the appeal, and set out a number of key points of planning principle which have the potential to cause ripples for developers, which are summarised below.

  1. Physical incompatibility

The Supreme Court held that where a later permission means it is physically impossible to implement an earlier permission, the earlier permission can no longer be relied upon to permit further development.

  1. Multi-unit development & partial completion

Unless there is clear indication to the contrary, planning permissions for multi-unit development should be treated holistically rather than authorising a series of independent acts. However, the court made clear that this did not mean that it was necessary for a multi-unit development to be completed in order for the development to be lawful.

  1. Material change

While a later permission may render it physically impossible to undertake works pursuant to an earlier permission, this is ultimately a question of materiality, whereby a material change would render the earlier permission undeliverable, whereas a non-material change would not have the same effect.

  1. Variations to the whole

The court held, that in the case of a full planning permission, there may be cases where a developer seeks to alter certain elements of their scheme. In that scenario, there is no reason why an approved development scheme cannot be modified by an appropriately framed additional planning permission which covers the whole site and includes the necessary modifications (and will therefore need to be accompanied by relevant plans, drawings, reports etc.).

Our thoughts

The decision of the Supreme Court has highlighted the importance of being clear, at the outset, when seeking permission for a detailed application, that the end scheme will not materially differ from that which is being sought at the outset.

The case considered the principle of overlapping planning permissions, and saw the Supreme Court re-affirm the conclusions reached in the earlier Pilkington case. However, Hillside then went on to distinguish between two types of variation to an existing permission: firstly those changes which result in mere inconsistency with the original permission, and secondly those changes which would be “material”, resulting in a physical incompatibility with the original permission. Where changes are sought subsequently and those changes fall within the second “material” category, the court’s position is that variations would need to be addressed on a site wide basis, rather than through a standalone (‘drop-in’) permission for a part of a site.

Inevitably such applications will increase costs for applicants owing to the enlarged site areas, the potential consequences for updated reports, and the administrative burden of notifying every landowner affected (which could conceivably include all existing plot purchasers).

However, where such changes are desired, developers may wish to consider whether they can amend a scheme through applications under sections 73 and/or 96 of the Town and Country Planning Act 1990, rather than through the submission of a fresh site wide new application.

Where outline permission is sought, it would be prudent for developers to consider the description of the development, to ensure that the site can be delivered in stages, to ensure that the details approved are ultimately those that will be delivered, and that any subsequent amendments are not physically incompatible with those parts which are already approved.

Equally, seeking to ensure conditions are appropriately drafted to enable changes to be made under section 73 might allow for changes to be made without the need for a full fresh application.

Where the Community Infrastructure Levy applies, the phasing of development is likely to be of even greater importance to seek to avoid any need to submit a replacement application which covers the whole of a largescale development site.

At first glance, the decision in Hillside places greater focus on those involved in the drafting of planning applications and conditions to ensure sufficient flexibility (or scope for readily severable change) to avoid any risk of needing to make material changes which render approved development physically incompatible (and so undeliverable) as a consequence of any desired redesigns of sites which will have a material change on the overall development.

No doubt the decision will lead to future litigation concerning the circumstances in which amendments would constitute a “mere inconsistency” with the original planning permission (and so, in theory, be acceptable), and conversely the circumstances in which any change would tip the materiality threshold and so require a new application to be made.

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Anna has 15 years’ experience advising on all aspects of planning, compulsory purchase and highways law, acting for a variety of public and private sector clients throughout her career including landowners, promoters, developers, local authorities, central government agencies, regional development agencies, and various NHS Trusts.

Paul is a specialist planning solicitor who focusses on delivering practical solutions for his clients. His work covers all aspects of the planning process, from strategic advice and drafting section 106 obligations and other planning and infrastructure agreements through to planning appeals and advocacy.

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Published: 10th November 2022
Area: Real Estate & Planning

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