Michael Mansell v Tonbridge and Malling Borough Council [2017] EWCA Civ 1314
Mansell is an important Court of Appeal judgment on the use of a fallback position in planning decisions. It confirms that an alternative development does not have to be probable or likely before it can be a material consideration. A real possibility can be enough. The judgment is also widely cited for the correct approach to reading planning officer reports.
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- Neutral citation
- [2017] EWCA Civ 1314
- Court
- Court of Appeal (Civil Division)
- Judgment date
- 8th September 2017
- Judge
- The Chancellor of the High Court, Lord Justice Lindblom and Lord Justice Hickinbottom
- Case number
- C1/2016/4488
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What Mansell decided
Tonbridge and Malling Borough Council granted planning permission for four new dwellings on a site containing a large agricultural barn and a bungalow at East Malling. The proposal conflicted with the development plan, but the planning officer advised that there was a realistic fallback if permission were refused.
Part of that fallback relied on the Class Q permitted development rights then available for converting agricultural buildings to dwellinghouses, together with the possibility of replacing the bungalow. The council considered the proposed four-house scheme preferable to the more piecemeal development that could otherwise occur.
The Court of Appeal upheld the council’s decision.
A fallback must be real, not merely theoretical
The Court of Appeal confirmed that the key question is whether there is a real prospect of the fallback development being implemented if the preferred proposal is refused.
A real prospect does not mean that the fallback must be probable or likely. A possibility can be enough. The opposite of a real prospect is one that is merely theoretical.
Whether that test is satisfied is highly fact-sensitive and involves planning judgment. The court rejected a formulaic approach.
You do not always need a detailed fallback scheme or an existing permission
Mansell makes clear that there is no rule requiring every fallback to have an existing planning permission, a fully worked-up design or a formal statement from the landowner setting out exactly how it will be implemented.
In some cases that degree of evidence may be needed. In others it will not. Here the landowner’s intention to obtain residential development value from the site was clear, and it was reasonable to assume that available permitted development rights would be used if the preferred scheme was refused.
The Class Q ruling was based on the rules in force in 2016
The judgment also considered the detailed Class Q limits that applied at the time. The Court of Appeal held that the former 450 square metre limit in paragraph Q.1(b) applied to the cumulative floor space actually changing use, rather than the total size of the agricultural building.
Those historic Class Q thresholds are no longer the current rules. The point is still useful when reading Mansell, but anyone considering a barn conversion now should use the current Class Q guidance. Planning Geek keeps the pre-21st May 2024 Class Q rules separately for older cases and decisions.
Mansell and planning officer reports
Mansell is also one of the authorities most often cited when a planning challenge attacks an officer report.
The Court of Appeal said officer reports should not be read with undue rigour. They are written for councillors with local knowledge and should be read fairly and with reasonable benevolence.
The question is whether, reading the report as a whole, the officer materially misled members on something bearing on their decision and whether that error went uncorrected. Minor or inconsequential errors can be excused. The court will intervene only where the advice contains a distinct and material defect capable of affecting the decision.
Planning law should not become excessively legalistic
Lord Justice Lindblom also warned against excessive legalism infecting the planning system. Planning decisions are not court judgments, and both national and local policy should be applied with good sense rather than subjected to unnecessary doctrinal complexity.
That does not excuse a material error of law. It explains why courts read planning decisions and officer reports in a practical way rather than looking for minor drafting imperfections.
Read the full Mansell judgment
The approved Court of Appeal judgment is held in the Planning Geek case law library. Gold Members can open the protected PDF below. If you are not signed in with Gold access, the button will take you to the appropriate membership option.
Related Planning Geek guidance
Our main guide to the subject is fallback position in planning. For the committee-report principles, see planning officer reports. If the fallback involves an agricultural building, use the current Class Q page rather than relying on the historic thresholds discussed in Mansell.
Mansell Case Law Page Updated: 9th September 2026