Mikael Armstrong v Secretary of State for Levelling Up, Housing and Communities & Anor [2023] EWHC 176 (Admin)
Armstrong section 73 is an important Planning Court judgment rejecting the idea that section 73 is legally limited to “minor material amendments” or changes which are not fundamental.
The statutory limit is different: section 73 cannot be used to alter the operative description of the development, but a substantial change to conditions is not unlawful merely because it is substantial.
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- Neutral citation
- [2023] EWHC 176 (Admin)
- Court
- High Court, King's Bench Division, Planning Court
- Judgment date
- 27th January 2023
- Judge
- James Strachan KC, sitting as a Deputy High Court Judge
- Case number
- CO/1288/2022
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What Armstrong decided
The case concerned a permission for the construction of one dwelling at Portwrinkle in Cornwall. A later section 96A decision added an approved-plans condition, after which a section 73 application proposed a substantially redesigned house.
The Inspector treated the proposal as too fundamental for section 73 and dismissed the appeal.
James Strachan KC, sitting as a Deputy High Court Judge, held that this was an error of law and quashed the decision.
Section 73 is not legally confined to minor material amendments
The phrase minor material amendment is commonly used in planning practice and guidance, but it is not a statutory limit written into section 73.
The court rejected a separate test asking whether the proposed variation was fundamental or substantial. If Parliament had intended such a restriction, it could have said so.
The operative description still cannot be changed
Armstrong did not displace the Court of Appeal’s decision in Finney. A section 73 permission must still authorise the same development described in the operative part of the earlier permission.
In Armstrong the operative description was broad: construction of one dwelling. The redesigned dwelling did not require that description itself to be changed.
The question was therefore whether the altered conditions could lawfully regulate that same development, not whether the visual changes felt major.
The later Court of Appeal approved Armstrong
The Court of Appeal subsequently revisited the issue in Test Valley Borough Council v Fiske [2024] EWCA Civ 1541 and expressly agreed with Armstrong’s analysis.
Test Valley confirms that section 73 is not subject to a separate substantial or fundamental alteration test. It also makes clear that neither the operative wording nor a condition on the new permission may contradict the operative grant of the earlier permission.
Section 73B is still not in force
Section 73B was inserted into the 1990 Act to create a future route for permissions which are not substantially different from an existing permission. As at 10th September 2026, that provision has not been brought into force.
That makes the existing section 73 case law particularly important when deciding whether an amended scheme can be dealt with through conditions or needs a fresh planning application.
Why Armstrong matters in practice
Do not ask only whether an amendment is major or minor. First identify exactly what the operative part of the existing permission authorises.
If the proposed change requires that grant itself to be rewritten, section 73 is not the route. If the operative description remains intact, the scale of the change to conditions is not by itself a statutory bar, although the planning merits still have to be assessed.
Read the full Armstrong judgment
The full Planning Court judgment is held in the Planning Geek case law library. Gold Members can open the protected PDF below.
Armstrong Section 73 Case Law Page Updated: 10th September 2026