Tiwana Construction Limited v Secretary of State for Housing, Communities and Local Government & Anor [2025] EWHC 1485 (Admin)
Tiwana unilateral undertaking is an important Planning Court judgment on late planning obligations, affordable housing and an Inspector’s duty to consider an obviously material planning benefit.
The High Court held that the Inspector acted unlawfully by deliberately disregarding an executed unilateral undertaking submitted before the appeal decision. The affordable housing it offered was an obviously material consideration, and the decision letter also failed to explain why it had been left out of account.
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- Neutral citation
- [2025] EWHC 1485 (Admin)
- Court
- High Court, King's Bench Division, Planning Court
- Judgment date
- 24th June 2025
- Judge
- Mr Justice Eyre
- Case number
- AC-2024-LON-003210
What Tiwana decided
The case concerned an appeal for ten self-build homes at Burwell. One of the council’s refusal reasons was the absence of affordable housing and a completed planning obligation.
At the hearing the Inspector indicated that three affordable homes would count positively in the planning balance. A section 106 agreement was being negotiated, but execution was delayed. On the final deadline the appellant therefore submitted an executed unilateral undertaking, accompanied by detailed legal submissions and a proposed Grampian condition.
The Inspector deliberately chose not to consider the undertaking or the affordable housing benefit. Mr Justice Eyre held that this was unlawful. Both the reasons challenge and the material-consideration challenge succeeded, and the appeal decision was to be quashed.
An executed unilateral undertaking can be just as legally real as a section 106 agreement
The court rejected any suggestion that there was something legally special about securing the benefit through a bilateral section 106 agreement rather than a unilateral undertaking.
The Planning Inspectorate’s own training material recognised that the two mechanisms can have equal legal status. A section 106 agreement may sometimes be preferable in practice, but the important question is whether the obligation offered is capable of securing the relevant planning benefit.
Planning Geek’s guides to unilateral undertakings and section 106 agreements explain the difference.
A planning consideration can be material without being decisive
The Inspector’s witness evidence suggested that affordable housing did not need to be considered because the appeal was going to be dismissed for other reasons.
The court rejected that approach. Whether a consideration is material and whether it ultimately changes the result are different questions.
If a matter is obviously capable of carrying weight in the planning balance, rational decision-making requires it to be considered. The decision-maker can then decide what weight it deserves and whether it changes the outcome.
The Inspector herself had identified affordable housing as important
The importance of the undertaking was especially clear because affordable housing had been one of the council’s refusal reasons and the Inspector had herself raised its positive value at the hearing.
An earlier draft decision letter treated provision of the affordable homes as a benefit of moderate weight. The final letter removed that analysis altogether.
The High Court held that the later executed undertaking addressed precisely the issue which had already been identified as important. It could not rationally be ignored merely because the Inspector had set a deadline for a different form of obligation.
The reasons failure caused real prejudice
The final decision letter did not explain why the unilateral undertaking had been disregarded. That was not simply clumsy drafting: the Inspector had deliberately chosen to sidestep the affordable-housing issue.
The claimant was therefore left unable to understand the true basis of the decision or properly assess whether it was lawful. The court found substantial prejudice.
Later witness evidence from the Inspector could explain what had happened factually, but it could not retrospectively supply reasons which the statutory decision letter itself was required to contain.
Simplex did not save the decision
The Secretary of State argued that the result would have been the same even if the undertaking had been considered.
The court accepted that the appeal probably would still have been dismissed, but that was not enough. To refuse relief on the Simplex basis, the court would need to be satisfied that the decision would necessarily have been the same.
Because the undertaking might have altered the weight given to affordable housing, that high threshold was not met.
Why Tiwana matters
The judgment is useful whenever a planning obligation is being finalised after an appeal hearing. Deadlines matter, but they do not automatically make an executed obligation irrelevant if it arrives before the decision and addresses an important planning issue.
It is also a strong reminder that an Inspector cannot avoid an obviously material consideration simply because it is unlikely to be determinative.
Read the full Tiwana judgment
The full Planning Court judgment is held in the Planning Geek case law library. Gold Members can open the protected PDF below.
Tiwana Unilateral Undertaking Case Law Page Updated: 10th September 2026