The case of Hillside Parks Limited v Snowdonia National Park Authority [2019]  is a useful reminder that the value of a site-wide planning permission can effectively be extinguished where the grant and initiation of subsequent planning permissions has rendered it impossible to complete the original development as planned.

Small scale residential development & planning permission

It was not uncommon to see planning permission granted for small scale residential development where it was understood that the scheme would be built out plot by plot over an extended time period (in excess of 20 years in some cases). Such sites or individual plots will then come to market, being sold with the benefit of an extant planning permission. This case is a caution to would-be developers and their professional advisors as to the extent to which such dated permissions can actually be relied upon.

The history behind the Hillside case | planning permission

In the Hillside case, only 41 dwellings out of a possible 401 had been constructed in the period between 1967 and 2017, when a declaration was sought and obtained confirming that the remaining dwellings could lawfully be completed under the original planning permission.

The point of challenge from the planning authority was that it had granted a number of planning permissions at the site after 1967 and indeed very little of the original scheme had been built according to the original plan, much of what had subsequently been consented conflicted with that plan and, as a matter of fact and judgement, it would now be impossible to complete the development according to the scheme consented in 1967.

The developer, perceiving considerable value in being able to complete the remaining 300+ houses without needing a fresh grant of planning permission, sought to rely on case law to the effect that where a planning permission authorised a number of independent acts of development (in this case the building of clusters of houses), each act was able to be carried out independently of the question of whether any of the other acts could also be carried out at that time.

The Judge’s decision

The judgement, finding for the authority and against the developer, was as much pragmatic as legal. The judge considered that what the original planning permission had authorised was a coherent development scheme for the whole site and either it was to be carried out according to that scheme (including an approved masterplan) or it wasn’t. The judge didn’t believe that the planning permission was for independent acts of development, whether clusters of houses or individual plots and so the case law relied on by the developer didn’t apply, and indeed the Supreme Court later held the view that the case law relied upon on this point had been wrongly decided. Practically, too, the intervening works (pursuant to separate planning permissions) had in effect now rendered it impossible to build out the 1967 scheme as approved. Although not explored in this level of detail, it may have been the case that an individual plot (perhaps the subject of an individual purchase by a self-builder) would have been capable of being constructed in accordance with the masterplan. However, since the planning permission here related to the entire site, the questions is not whether parts of it can be aligned with the original plans but whether the development as a whole can be so completed.

The judge did comment that what was proposed was not a ‘minor deviation’ from the approved masterplan. That clearly leaves the door open, if only a little, but each case would need to be judged on its facts at the time. Elsewhere, extreme caution ought to be exercised in cases where the value of a site derives from an extant, but rather old, planning permission and, importantly, other consents have been granted and implemented on the site in the interim.


In the later proceedings, the developer sought to make some ground on the basis that the later applications and permissions had been “variations” of the earlier consent (and that word had indeed been widely used). Two points arose at the Supreme Court: Firstly, that that wasn’t an argument that had been pursued earlier and no plans or documents were before the lower courts. Secondly, and of wider interest, that as a matter of law it was not possible for a later full planning permission to “vary” an earlier planning permission.

The note of caution about relying on an old but incomplete permission remains. However, the Supreme Court did offer some slight clarification in terms of completed works. It had been suggested (from the Court of Appeal’s judgement) that the early properties might have been unlawful as a result of the inability to or failure to complete the full scheme. Had it been left at that, it could have caused considerable disquiet for the buyers of properties in early phases of a development scheme. The Supreme Court confirmed that the failure or inability to complete a project does not make development carried out in an early phase pursuant to that permission unlawful.


If you have any situations involving planning permissions feel free to contact our Real Estate team.