What does Hillside mean for future permissions?

When there is more than one permission for a plot of land, does the law allow the site owners to complete both works – or is the situation more complex?


  • Richard Kimblin

23 November 2023

Aberdovey, Snowdonia, looking up the estuary

On a hill near Aberdyfi in the Snowdonia National Park is a housing development that has been built at glacial pace.

A full planning permission with a detailed masterplan was granted in 1967 for 401 dwellings. But by 1987 only 19 of these had been built, none of which were located in accordance with the masterplan.

To date, only 41 houses have been built, and all were the subject of eight specific and subsequent planning permissions. In 2017, the Snowdonia National Park Authority wrote to Hillside, the owner of the land, arguing that, 50 years on, it was impossible to implement the permission further.

While these bare facts are only summarised here, we should note just how unusual they are in a residential development context.

Permissions subject to repeat legal action

There are four judgments about the underlying permission, in two cases. The first was in 1987 when the then developer sought a declaration from the High Court as to whether the 1967 permission remained valid. The court declared that it was (unreported).

In 2019, the issue arose for a second time because the developer went back to court in Hillside Parks Ltd v Snowdonia National Park Authority [2019] EWHC 2587 (QB), to seek a declaration to resolve the dispute over whether it was now possible further to implement the permission. This time the planning authority was successful.

The developer went to the Court of Appeal in Hillside Parks Ltd v Snowdonia National Park Authority [2020] EWCA Civ 1440 and was again unsuccessful. The essence of that decision was that the judge was entitled to conclude that, in the light of factual developments since the 1987 case, it is no longer possible to implement the 1967 permission.

In turn, the developer appealed to the Supreme Court. Its argument in Hillside Parks Ltd v Snowdonia National Park Authority [2022] UKSC 30 was that further development on the vacant parts of the site could still lawfully be carried out.

Context set by 1990 Act and key cases

It is important to bear some familiar principles in mind, as the Supreme Court reminded itself at paragraphs 19–27:

  • The definition of development in section 55 of the Town and Country Planning Act 1990 'the carrying out of building, engineering, mining or other operations in, on, over or under land, or the making of any material change in the use of any buildings or other land.' In this case we are concerned with the former type of development (operational development) and not with change in use.
  • A permission is simply that – the 1990 Act does not impose an obligation to build what is permitted.
  • Permission runs with the land.
  • A permission may be varied in the sense that a new permission may be granted that does not require compliance with a condition on a the permission: see section 73 of the 1990 Act and further, non-material amendments in section 96A
  • The meaning of a planning permission should be ascertainable from the permission itself and other public documents to which it refers, such as plans: for example in Trump International Golf Club Scotland Ltd v Scottish Ministers [2016] 1 WLR 85, paragraphs 33–34 (Lord Hodge JSC).

There are two decided cases that provide the foundations for the Supreme Court's decision.

Pilkington v Secretary of State for the Environment [1973] 1 WLR 1527 concerned the owner of a plot of land who was granted planning permission to build a bungalow on that plot. After the bungalow was built, he discovered an earlier planning permission granted to the previous owner to build a bungalow on a different part of the same plot.

The description of the development in the earlier permission and the relevant plan showed that the rest of the plot was to be used as a smallholding. The question was whether a further bungalow could lawfully be built in the location specified in the earlier permission.

If a consent is implemented but there is a second consent and the question is whether it is lawful to develop according to the latter, the test is 'whether it is possible to carry out the development proposed in that second permission, having regard to that which was done or authorised to be done under the permission which has been implemented'.

Pioneer Aggregates (UK) Ltd v Secretary of State for the Environment [1985] AC 132 meanwhile is a judgment of the House of Lords establishing that there is no principle in planning law by which a planning permission may be abandoned. A member of the public should be able to ascertain the existence of a valid planning permission by inspecting the planning register and the land.

Supreme Court sets key future principles

There are nine essential principles to take from the Supreme Court's judgment, which we can apply in future development management decisions.

  • It is the duty of the local planning authority to regard every application for planning permission, unless it refers to an earlier permission, as a proposal for a separate and independent development and to consider the application on its own merits.
  • There is no statutory condition precedent or subsequent that a permission be implemented in full.
  • Failure or the inability to complete a project for which planning permission has been granted does not make unlawful any development that has already been carried out pursuant to that permission.
  • There is then the question of whether part of the permission may be separated and treated independently of the remainder – severance. In the absence of clear express provision making it severable – a planning permission is not to be construed as authorising further development if at any stage compliance with the permission becomes physically impossible.
  • The ordinary presumption must be that a departure will have this effect only if it is material in the context of the originally permitted scheme as a whole.
  • For a development to fall foul of the principles in Hillside means that development which is already carried out makes it impossible to implement the second permission in accordance with its terms. Mere incompatibility with the terms of another, implemented, permission does not mean that a permission that is capable of being implemented is of no effect.
  • The reason why further development relying on a permission that cannot physically be carried out does not comply with section 57(1) of the 1990 Act is that the development would in effect not have permission.
  • Permission for a multi-unit scheme must be sought and granted for that development as an integrated whole.
  • Implementation of a permission that makes completion of a multi-unit scheme impossible is likely to make further implementation of that scheme unlawful.

Judgment has bearing on minerals permissions

The Supreme Court was concerned with a development for a substantial number of dwellings in accordance with a masterplan; that is, built development that was due to proceed unit by unit along with the associated infrastructure. In contrast, much minerals development includes no permanent built development. It proceeds by individual acts of development as the mineral is worked.

In a modern minerals permission, the outcome is a landform that is a part of the permission itself, subject to restoration conditions. How that landform is produced, the progress of working, temporary landforms and methods of winning the mineral are usually the subject of planning conditions.

The Supreme Court in Hillside is not concerned about compliance with planning conditions; this is clear from the discussion of Pilkington. In that case, the court specifically avoided a conclusion on the basis of a failure to comply with a condition. Rather, Hillside is about permissions for a whole development, and concerns what happens part-way through implementation of the first permission when a second comes along.

Sometimes a minerals operator may lose part of a site due to intervening circumstances, such as a compulsory purchase order or because the operator itself revises its intended use of part of the consented land.

The first point to make is that such an intervening event does not make the development to date unlawful.

The second is that there is no legal obligation to complete a development save in respect of restoration requirements where they pertain, which they almost always will for minerals and waste schemes. So there is no obligation to work the mineral at a location that is now required for the second permission.

The third point is that there is no automatic consequence that a second permission renders the first incapable of further implementation. In other words, it does not automatically mean that working under permission 1 becomes unlawful. Rather, the question is whether implementation of permission 2 would make continued working under permission 1 physically impossible.

'The Supreme Court in Hillside is not concerned about compliance with planning conditions; this is clear from the discussion of Pilkington'

What has Hillside changed?

For the minerals and waste sectors, the practical impact of Hillside is much less than for built development, particularly larger and phased residential schemes for which questions of severance will often arise and may be difficult to justify in the context of the original masterplan. Such schemes are also often derived from an outline planning permission whereas the outline planning permission is unknown to minerals planning.

Hillside affirms Pilkington, a judgment that we have had for 50 years. It explains that what you see is what you get, and what you got was what you asked for. The planning authority assessed what you asked for, not your change of mind, which could perhaps be years later. But what you have done in accordance with permission will be fine.

You can run two permissions on the same land, but only so long as the second does not make it physically impossible to implement the first. You can always apply to change the first scheme. But the issue of applying to carry out development without compliance with a condition on a planning permission under section 73 of the 1990 Act would require a whole other article.

Richard Kimblin KC is a barrister at No5 Chambers

Contact Richard: Email | LinkedIn

Related competencies include: Masterplanning and urban design, Minerals management, Planning and development management

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