Deemed planning permission: HS2 tunnel appeal heads to Supreme Court

The Supreme Court has granted HS2 Ltd permission to appeal against a ruling that the Bromford Tunnel Extension does not benefit from the special deemed planning permission attached to the High Speed Rail (London-West Midlands) Act 2017.

The appeal asks whether the revised tunnel works were “covered” by the Environmental Statement prepared for the hybrid Bill. The answer could affect how the Act’s planning regime applies when HS2 Phase One designs change after Parliament has considered the project.

Permission to appeal is a procedural step, not a decision on the merits. The Supreme Court has not ruled that the tunnel has planning permission, and the Court of Appeal’s declaration remains the outcome unless and until it is changed on appeal.

What the Supreme Court has agreed to hear

The Court’s case page for UKSC/2026/0119 records that permission was granted on 29th September 2026. The issue is whether the Bromford Tunnel Extension and its relocated eastern portal benefit from deemed planning permission because they were “covered” by an Environmental Statement for section 20(2)(c) of the 2017 Act.

The appeal follows a unanimous Court of Appeal judgment in R (North Warwickshire Borough Council) v Secretary of State for Transport and another [2026] EWCA Civ 832. The full judgment is available on The National Archives’ Find Case Law service. Lord Justice Holgate, with Lady Justice King and Lord Justice Bean, decided that the revised works were authorised by the 2017 Act but did not benefit from its deemed planning permission.

Those are separate statutory questions. The first asks whether the Act authorised HS2 to build the revised works. The second asks whether the permission which the Act deems to grant for certain authorised development also covers those works. The Court of Appeal answered the first question yes and the second no.

How the tunnel design changed

The 2017 Act authorised the construction and maintenance of HS2 Phase One. Its deposited plans and Environmental Statement assessed a route through North Warwickshire involving embankments, a viaduct and a shorter Bromford Tunnel. As detailed design progressed, HS2 Ltd proposed replacing part of that arrangement with a tunnel extension of about 2.9 kilometres and moving the eastern portal towards Water Orton.

The amended design was not itself listed among the Act’s scheduled works. HS2 relied on section 2, which authorises certain non-scheduled works for Phase One, and on section 20, which provides a deemed planning permission for development authorised by the Act, subject to statutory exceptions.

North Warwickshire Borough Council challenged a 14th May 2024 decision by the Secretaries of State approving the portal works under Schedule 17. The council argued that the extension was outside the Act’s construction powers and, separately, that it lacked deemed planning permission. The High Court rejected the challenge in May 2025. The council then appealed.

Authorised to build, but without the Act’s permission

On the first issue, the Court of Appeal rejected the council’s challenge. It held that the tunnel extension and portal were authorised by the broad non-scheduled works power in section 2(1). The fact that the detailed design differed from the scheme assessed by Parliament did not, by itself, place the works outside that statutory power.

But that conclusion did not settle the planning-permission question. Section 20 creates a separate statutory route to planning permission. For non-scheduled works, its operation depends on the conditions in section 20(2), including whether the works were covered by an environmental assessment connected with the Bill. The court read that provision with section 68(4), which defines when development is covered by such an assessment.

The Court of Appeal rejected the government’s approach that the revised scheme could count as covered because its likely significant effects were no greater or different from those already assessed for the earlier design. The Court rejected a comparison between the likely significant effects of the revised works and those assessed for a different design in the same part of the project as the legal test.

Instead, the statutory question turns on whether information about the development in question was contained in a deposited statement which constituted an Environmental Statement when it was deposited or published. The Court concluded that Parliament had not assessed the amended tunnel works themselves through the original Bill documents. It therefore declared that the deemed permission under section 20(1) did not apply to the Bromford Tunnel Extension and eastern portal.

Why the distinction matters beyond Bromford

The decision does not say that HS2 lacked statutory authority to build the revised works. Nor did the Court of Appeal quash the Secretaries of State’s decision: North Warwickshire sought declaratory relief, and the works had already substantially progressed. The ruling instead separates the Act’s construction powers from the planning permission normally needed for development.

If works are authorised by a hybrid Act but fall outside its deemed permission, a separate planning permission may be required under the Town and Country Planning Act 1990, with environmental assessment considered under the applicable regulations. The precise approvals needed will depend on the works and the relevant statutory route; the Court of Appeal’s judgment did not determine a future application for permission.

The Court recorded that its construction of sections 2 and 20 could be relevant to the treatment of revised designs elsewhere on HS2 Phase One. That gives the Supreme Court appeal significance beyond this particular tunnel: promoters and planning authorities need to understand how far the Act’s streamlined consent arrangements extend when detailed designs change.

The judgment also stressed that this legal distinction should not become a means of obstructing a nationally important project. Lady Justice King said the appeal could not be “seen as a means by which those who still object to the Phase One project may improperly seek to impede or materially delay its execution”. The court also emphasised efficient cooperation between HS2 Ltd and local planning authorities.

Separate Supreme Court case has a different record

The Supreme Court has linked the matter to UKSC/2026/0118, brought by the Secretaries of State. Its cases listing labels that application “Permission to Appeal application lodged”. However, the linked case detail page also records a permission decision dated 29th September 2026 as “Granted”. The court’s online records therefore do not present a consistent status for that linked application. This article reports the clearly recorded grant in HS2 Ltd’s UKSC/2026/0119 case and does not assume the two entries have identical procedural status.

The Supreme Court’s case summary says the tunnel extension has gone into construction and that the council has not sought enforcement action. The permission decision itself does not alter the Court of Appeal’s outcome. The Supreme Court will decide the statutory interpretation issue only after the appeal process has run its course; no hearing date or judgment date is listed on the case page.

Why deemed planning permission is a separate question

The case is a reminder that statutory authority to carry out works and planning permission for those works can operate through distinct legal provisions. For hybrid Acts, the scope of the environmental assessment and the language of the deemed-permission provisions may matter as much as the breadth of the construction power.

For local planning authorities, infrastructure promoters and landowners, the practical issue is whether a revised design remains within the relevant statutory consent and whether separate permission or assessment is required. The Supreme Court’s decision will clarify the reach of section 20 for the Bromford works and may inform future questions about design changes on Phase One.

Read our guide to deemed planning permission for an overview of how permission can arise without a conventional planning application. Planning Geek is a planning consultancy: contact our planning team if you need planning-side advice or support coordinating specialist input.