Fallback position in planning and the real prospect test

A fallback position is a lawful alternative the applicant could carry out without the permission being sought, offered to the decision-maker as a comparator: refuse this, and what happens instead is no better, and quite possibly worse. It is one of the few arguments in planning that can defeat a policy objection without engaging the policy at all, and it is also one of the most frequently overstated.

The weight it carries depends almost entirely on one question. Is there a real prospect of the fallback actually being implemented?

What a fallback position is in decision-making

The logic runs like this. The decision-maker compares the proposal against what would happen if it were refused. Ordinarily that comparison is against the existing situation. Where a lawful alternative exists and would realistically be pursued, the comparison shifts to that alternative instead, and the harm attributable to the proposal is only the difference between the two.

Three routes create one.

• Permitted development rights under the General Permitted Development Order that the applicant could exercise without any application. Our note on what permitted development rights cover sets out the starting position.
• An extant planning permission capable of implementation.
• A prior approval already granted, which is a consent in its own right rather than a right the council has never examined. Our explainer on prior approval as the halfway house before permission covers how those work.

A fallback is not a threat and should not be written as one. Officers respond badly to statements that the applicant "will simply build the permitted development scheme instead", and inspectors respond worse. Set it out as a comparison of planning effects and let the comparison do the work.

The real prospect test

The leading authority is the Court of Appeal's decision in Mansell v Tonbridge and Malling Borough Council in 2017, where Lindblom LJ set out the approach. The question for the decision-maker is whether there is a real prospect of the fallback being implemented, as distinct from a merely theoretical possibility. The prospect does not have to be probable or more likely than not. It has to be real.

Two consequences follow, and they pull in opposite directions.

The bar is lower than people assume. An applicant does not have to prove they would build the alternative. They have to show that doing so is a genuine possibility, which is why a modest amount of evidence can be enough.

But the assessment is fact-sensitive and the decision-maker has a wide margin. An inspector who concludes that a fallback is fanciful is unlikely to be overturned, because the judgement is one of planning rather than law.

What that means for drafting: put the evidence in, and do not rely on the legal proposition alone. A page of case law with no evidence about the site is worth less than half a page of evidence with a single citation.

Evidencing a permitted development fallback

The strongest version of this argument is one where somebody at the council has already agreed the alternative is lawful.

1. Apply for a certificate of lawfulness for proposed use or development under section 192 of the Town and Country Planning Act 1990 for the fallback scheme, and obtain it before, or alongside, the main application.
2. Draw the fallback scheme properly, to the same standard as the proposal, so the comparison is like for like rather than a sketch against a designed building.
3. Show that the fallback is physically and commercially deliverable: access, levels, structural condition, and where relevant a costed indication that it is a rational thing to do.
4. Deal with the conditions and limitations attached to the class relied on, because a fallback that breaches a limitation is not lawful and therefore is not a fallback.
5. State the applicant's position on intention honestly, without overstating it.

The certificate is the single most effective step. It converts an argument about whether something is lawful into a fact, and it leaves the council arguing only about likelihood.

Set the comparison out in the Planning Statement as a table of effects: scale, siting, appearance, overlooking, landscape impact, traffic. Where the fallback is worse on a given effect, say so plainly. Where it is better, say that too, because a comparison that finds the fallback worse on every measure reads as advocacy rather than analysis.

Extant permissions as a fallback

An unimplemented permission with time still to run is a straightforward fallback, provided it can actually be implemented.

Check four things before relying on one.

Whether the time limit has expired, and whether any material operation has been carried out that lawfully began the development. A permission lawfully begun does not expire, which is why a started scheme is a durable fallback.

Whether all pre-commencement conditions can still be discharged. A permission with an unsatisfiable pre-commencement condition, for example one requiring a survey in a season that has passed or an agreement the applicant cannot obtain, may not be implementable.

Whether any consent outside planning is missing: listed building consent, a protected species licence, a highway agreement under section 278.

Whether the land control needed for the fallback exists, particularly where the earlier permission relied on visibility splays over third-party land.

In the Green Belt this argument does real work, because an extant permission for inappropriate development can reduce the harm attributable to a new proposal. It does not remove the need to demonstrate the case, and our note on very special circumstances in the Green Belt covers what else has to be shown.

Where fallback arguments overreach

Four failure modes recur.

The fallback is theoretical. The applicant has no interest in a 40 cubic metre roof extension and has said so in correspondence, which the council has read.

The fallback is not lawful. The scheme relied on breaches a limitation in the class, sits on Article 2(3) land where the class is excluded, or depends on rights removed by an Article 4 direction or by a condition on the original estate permission.

The fallback would need a consent that has not been obtained, so it could not be built even if the applicant wanted to.

Or the comparison is drawn between a carefully designed proposal and a deliberately unattractive fallback. Inspectors notice. Where the fallback is drawn to look as bad as possible, the argument tends to be given less weight rather than more.

An illustrative example on a Class Q site

Illustrative example. A steel-framed agricultural building with a prior approval granted for conversion to two dwellings under Class Q, and a new application for two replacement dwellings of better design and slightly different siting.

The fallback is strong here for specific reasons. The prior approval is a granted consent, not an assumption. The Class Q scheme is drawn and assessed. It would produce two dwellings in the same location, with the same access and the same trip generation, in a building of poor appearance. The proposal delivers the same number of homes in better designed buildings, and the landscape effect is comparable or better.

The applicant's evidence is the prior approval decision notice, the approved drawings, a construction feasibility note confirming the frame can carry the conversion, and a short statement on programme. That package makes the prospect real rather than theoretical.

Change one fact, let the prior approval lapse, and the argument collapses to a theoretical possibility that would require a fresh application nobody has made.

Enter your postcode on PlanScope to see which reports a site is likely to need. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. This is general guidance rather than legal advice, and a lawful development certificate is the only formal way to confirm that works are lawful.