The High Court has quashed an appeal decision after an Inspector treated significant highway impacts as a major reason for refusal despite finding that the residual cumulative traffic effects would not be “severe”.
Greystoke CB Limited v Secretary of State for Communities, Housing and Local Government & Anor [2026] EWHC 1997 (Admin) is an important reminder that the NPPF highway refusal threshold cannot be acknowledged in one part of a decision and then disappear when the final planning balance is carried out.
There is a second useful point too. The Inspector found that the scheme would deliver 23% biodiversity net gain for habitats and 10% for hedgerows and treelines, but did not include that benefit in the planning balance. The court held that ground succeeded as well.
What was the Banbury proposal?
The case concerned agricultural land east of Junction 11 of the M40 and south-west of Huscote Farm at Banbury. Greystoke sought outline permission for up to 140,000 square metres of B8 employment floorspace, with ancillary offices, infrastructure, accesses, roads, landscaping and other works.
Cherwell District Council refused the application in March 2024, giving 15 reasons. Highway congestion, capacity and safety featured heavily. Greystoke appealed and a nine-day inquiry followed in February 2025.
The Inspector dismissed the appeal in July 2025. The important twist is that, by the time he reached his conclusions, he did not find the test in paragraph 116 of the NPPF to be met. Highway safety was not unacceptable and the residual cumulative impacts on the road network were not severe.
The NPPF uses a high threshold for refusing on highway grounds
The NPPF says development should only be prevented or refused on highway grounds where there would be an unacceptable impact on highway safety, or where the residual cumulative impacts on the road network following mitigation would be severe.
That wording matters. It does not mean that congestion below the “severe” threshold suddenly becomes irrelevant. A decision-maker can still consider the effect of traffic, the adequacy of mitigation, conflict with local policy and the wider material considerations.
What the Inspector could not lawfully do was find the national refusal threshold was not crossed, then give the unresolved highway effects substantial weight as the dominant factor against the development without bringing that NPPF policy back into the final balance.
Highways did not have to be the only reason for refusal
The Secretary of State argued that the NPPF threshold was not decisive because the appeal had not been dismissed solely on highway grounds. Other harms included location, landscape and heritage.
Mr Justice Coppel rejected that narrow reading. Paragraphs 115 and 116 had to be read together. Where the highway effects were the principal or dominant reason weighing against permission, the Inspector had to grapple with the policy saying development should not be refused on highway grounds unless the specified threshold was reached.
The judgment is therefore not a rule that every scheme with “less than severe” traffic impacts must be approved. Nor does it prevent a decision-maker departing from national policy where there is a rational planning reason to do so. The problem in Greystoke was that the Inspector did not perform that exercise at all.
The biodiversity net gain was also left out of the balance
The Inspector separately found that the development would achieve 23% BNG for habitats and 10% BNG for hedgerows and treelines. Those figures appeared in the ecology section of the decision but not among the benefits weighed in the planning balance.
For the purposes of the case, the Secretary of State invited the court to assume, without finally deciding the wider legal point, that BNG was a material consideration which the Inspector was required to take into account. On that basis, the court found that he plainly had not done so.
This point needs a little care. Greystoke should not be quoted as establishing a universal rule that every BNG figure must always receive positive weight in every planning decision. What it does establish on the case as argued is much simpler: once the Inspector was required to take this particular BNG benefit into account, finding it in one section and omitting it from the actual balance was not enough.
Our main guide explains the statutory system for biodiversity net gain.
Why was the decision quashed?
The High Court allowed the challenge on the NPPF highway ground. It also allowed the BNG ground, although that produced no additional remedy because the appeal decision was already being quashed.
The consequence is that the appeal has to be reconsidered. That does not mean Greystoke automatically gets planning permission. The fresh decision-maker still has to assess all the harms, benefits, development-plan conflict and material considerations. But the highway threshold and the BNG finding must now be handled lawfully in that exercise.
What does Greystoke mean in practice?
- Read the NPPF highway assessment and refusal provisions together
- Do not treat a finding of significant traffic impact as though it automatically satisfies the separate “severe” refusal threshold
- If highway harm is the dominant factor against permission, explain how the national refusal threshold affects the final planning balance
- A decision-maker can depart from national policy, but must recognise the policy and give a rational reason for doing so
- Benefits identified in the evidence should not simply vanish when the final planning balance is written
- Where BNG is a material consideration in the particular decision, say what weight is given to it rather than merely recording the percentage
Primary source
This article is based on the full judgment in Greystoke CB Limited v Secretary of State for Communities, Housing and Local Government & Anor [2026] EWHC 1997 (Admin).
Created: 29th August 2026 | highway impact
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