Severability: when part of a permission survives

Severability planning permission questions arise at the worst moments. A client reads a condition, decides it is unlawful, and asks whether they can simply ignore it. Or a permission is challenged and the claimant attacks one element, and everyone wants to know whether the rest survives. The two situations use the same word and apply different tests.

The short answer on conditions is that severance is possible but narrow. A condition can be struck out and the permission left standing only where the condition is not fundamental to the grant. If it is fundamental, and it is unlawful, the permission goes with it.

Severing a condition

The approach the courts take asks whether the condition goes to the heart of the permission. Conditions that are incidental, tidying up detail or controlling a peripheral matter, can be severed without disturbing what was granted. Conditions without which the authority would plainly never have granted permission cannot.

The authorities that established this are familiar to anyone who has argued the point. A condition requiring an applicant to construct a road at their own expense and give rights of passage over it was held to be so unreasonable as to be ultra vires and inseverable from the permission. A condition requiring a personal permission tied to an occupancy restriction has been treated as fundamental on similar reasoning.

There is a related trap in conditions that purport to control land outside the application site, or to require the applicant to give up rights. Those tend to fail the lawfulness test and tend also to be fundamental, which is the worst combination available.

So the analysis runs in two steps, not one. First, is the condition lawful, applying the usual tests of planning purpose, relationship to the development and reasonableness. Second, if it is not, was it fundamental. The second question is the one people skip, and it is the one that determines whether the client still has a permission.

When the whole thing falls

A permission granted subject to an unlawful fundamental condition is vulnerable in its entirety. That is an uncomfortable position for a developer who has already implemented it.

Two practical consequences follow. A claimant challenging a permission may attack a condition precisely because the condition is fundamental, in the hope of taking the permission with it. And a developer who wins an argument that a condition was unlawful may find the victory hollow, because the court removes the permission rather than the condition.

That asymmetry is why advisers steer clients towards section 73 of the Town and Country Planning Act 1990. An application to vary or remove the condition produces a new permission subject to different conditions, decided on planning merits, with an appeal if it is refused. It does not require anyone to argue that the original decision was unlawful.

The section 73 route has its own limits. It cannot be used to change the description of development, and the authority reconsiders the condition rather than rubber-stamping the change, so an unfavourable policy shift since the original grant can work against you. But it leaves the original permission intact and available while the new application is decided, which is the point.

Partial quashing on judicial review

The court's remedial powers under the Senior Courts Act 1981 are discretionary, and partial quashing is available where the unlawful element can be separated from the rest.

Public law draws the distinction between textual severance, where the offending words can be excised leaving a coherent text, and substantial severance, where what remains is still in substance the decision the decision-maker made. Both usually have to be satisfied. A permission where the unlawfulness lies in a discrete condition may survive with that condition quashed. A permission where the officer's report misdirected the committee on the policy test infects the whole decision, and nothing survives.

Heritage cases illustrate the point. Where a committee has been misdirected on the heritage balance, the error runs through the whole assessment and severing a condition achieves nothing. Where the same permission carries a separate and unrelated condition that happens to be unlawful, that condition can go on its own.

Split decisions

A different question, often confused with severability, is whether an authority can grant permission for part of an application and refuse the rest.

The authority determines the application before it. Where a proposal is divisible, and the applicant agrees, a split decision is occasionally issued, and some authorities are more willing than others. The difficulty is that the resulting decision can be hard to interpret, particularly where the plans show a single scheme and the description of development covers both elements.

The practical advice is straightforward. If you can see that one element is likely to be resisted and the other is not, submit them as two applications. A shop conversion and a rear extension can be applied for separately. A single application covering both hands the authority a choice between refusing everything and issuing something nobody can implement cleanly.

Illustrative example: an application for a change of use plus a new mezzanine and a plant enclosure. The use was acceptable, the enclosure was not. Submitted as one application, it was refused in full and the applicant lost four months. Submitted as two, the use would have been granted while the enclosure was redesigned. That example is illustrative.

What it means for implementation

Three points matter on site.

Do not proceed on the basis that a condition is void. If the view is wrong, the development is unauthorised, and enforcement follows. The appeal route that then opens, including the deemed application on a ground (a) appeal, puts the whole scheme back into the planning merits arena on the authority's timetable rather than yours.

Watch the relationship with any planning obligation. A section 106 agreement is usually drafted by reference to the permission it relates to. Quashing that permission, wholly or in part, raises questions about what the obligation now binds, and well-drafted agreements address the scenario expressly.

And keep the commencement position under review. Implementation in reliance on a permission that is under challenge is a commercial decision rather than a legal protection.

Advising a client who thinks a condition is void

Work through it in order.

1. Read the condition against the tests for a lawful condition, and read the officer's report to see why it was imposed.
2. Ask whether the authority would plainly have refused permission without it. That is the severability question, and it is often answered in the committee report.
3. Consider whether a section 73 application would give the client what they want, faster and with less exposure.
4. Consider a certificate of lawfulness where the argument is that the condition does not bite on the proposed activity at all, which is a different point from invalidity.
5. Reserve judicial review for cases where the client accepts the risk that the whole permission may fall, and take the deadline seriously, because it is short.

Where the answer is a fresh application, the policy case has to be made from scratch, and a planning statement dealing openly with the history of the earlier condition tends to fare better than one that ignores it. You can see the supporting documents a fresh application needs before deciding which route to take.

This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.