The Supreme Court judgment in Hillside Parks shows that common sense helps operate the planning system in a practical and fair way.
It will stimulate calls for legislative change. The purpose and nature of that change should be considered very carefully, not least because it may be unnecessary given the things the judgment helpfully confirms:
- The test for overlapping permissions is a simple, factual, one
- A planning permission does not authorise development if and when, as a result of physical alteration of the land to which the permission relates, it becomes physically impossible to carry out the development for which the permission was granted (without a further grant of planning permission) […] in accordance with its terms.
- Mere inconsistency is not enough – development carried out must have made it impossible to implement the other permission. That does not refer to conditions but does apply to the whole site covered by the other planning permission which raises the stakes.
- There will be cases where this impossibility has simply not arisen, because the two permissions have been designed to be compatible (e.g. Robert Hitchins). There will be others where the permission is capable of being interpreted as ‘severable’ into moveable parts (see below). For others, there will need to be some tweaks or (as noted below) some caution.
- The ability to understand the permission from the planning register and the position on the site is critical  – everyone preparing applications and drafting permissions should have this in mind.
- It is not for LPAs to refuse to deal with overlapping permissions  – the choice is for the developer and each application should be dealt with on its own merits. Where Grampian conditions and S106 obligations are used sensibly, the relationship with a wider masterplan will be able to be managed so that the merits are straightforward.
- Multi-unit permission should not be seen as authorising individual acts across a wide masterplan, such that they can be ‘mix and matched’ with new slot-in permissions [68, 71]. The Lucas case was wrongly decided for adopting this as a starting point.
- BUT the Judgment is – crucially – crystal clear [46, 50] that this is “a question of interpretation” in each case. As a result, where it is clear that the permission does allow for independent acts (or zones) of development, the degree of severability needed to ‘mix and match’ can be achieved by sensible, collaborative drafting of the permission (and any NMA properly capable of being used to achieve the same thing).
- Development remains lawful where partially completed (and is not rendered unlawful in the round due to specific departures).
- The Judgment finally puts unhelpful (and unnecessary) comments made in the High Court and Court of Appeal on the Sage case into the right perspective [63/64, 66].
For legal geeks, the Judgment also helpfully reminds that (in line with Lever Finance ), non-material departures from the approved plans are already inherent in the permission. The Section 96A TCPA 1990 Non Material Amendment route is just a confirmatory regime  (albeit one that is very helpful).
Those acquiring development land with permission, or selling land parcels off, will need to ensure that the permission is clearly intended to operate in severable parts (e.g. independent development zones). Permission will need to be structured, and in some cases amended, to ensure this is both clear and practically effective. Where this is not the case, there is a real risk that a party without control of the wider site could lose its ability to develop out under the permission it has acquired with the benefit of. Those acquiring sites will therefore need very clear protections, Certificates of Lawfulness and/ or amendments to existing permissions to ensure this is baked in.