Hillside Parks Ltd (Appellant) v Snowdonia National Park Authority (Respondent) 2022 UKSC, handed down in November 2022, raises important issues in planning law regarding the relationship between successive grants of planning permission for development on the same piece of land.

This case dates back to 1967, with the first set of proceedings being brought in 1985, finally reaching the Supreme Court on appeal in 2022. Planning permission was granted for a “large housing estate of 401 dwellings in Snowdonia National Park. The approved plan identified the proposed location of each house and the road system for the estate”. The appellant, Hillside Parks Limited (Hillside) is the current owner and developer, having acquired it in 1988. Since the 1967 Permission was granted, only 41 houses have been built on the Site, none in accordance with the original approved plan.

Following the Hight Court trial, in 1987 Drake J granted a number of declarations, including one that “development under the 1967 Permission could still be lawfully completed in accordance with the Master Plan “at any time in the future””. Further planning permissions were then granted by the local authority relating to other parts of the site, which departed from the original approved plan. It subsequently came to light that properties had been built on an area of the site that had no planning permission, and in a manner inconsistent with the original approved plan.

Hillside were informed by the local authority in 2017 that it “could not now implement the 1967 Permission given that it was not physically possible to build the development in a manner consistent with the Master Plan”. Proceedings were duly brought seeking declarations that the 1967 Permission remained valid and could be carried out to completion as set out in the 1987 Declaration. At first instance Hillside’s claim was dismissed by the High Court ([2019] EWHC 2587 (QB)). Hillside’s appeal to the Court of Appeal was unsuccessful ([2020] EWCA Civ 1440). Hillside has now appealed to the Supreme Court, which was also unsuccessful and unanimously dismissed.

In this decision, the Supreme Court has re-affirmed the so-called ‘Pilkington principle’, the “leading case on the effect of successive and mutually inconsistent planning permissions granted for development on the same site (Pilkington v Secretary of State for the Environment [1973] 1 WLR 1527)”. Essentially, where development is carried out on land which is incompatible with an extant planning permission, that permission can no longer be relied on as authorising further development. It is not automatically thus; there is required to be “material departure” from the permitted scheme.