Sentinel Estates Ltd v Secretary of State for Housing, Communities and Local Government [2026] EWHC 1122 (Admin)

Sentinel Estates is an important Planning Court judgment on HMOs and the former four-year enforcement rule. The court held, in the alternative, that although an HMO can be a dwellinghouse in planning law, use as an HMO is not use as a single dwellinghouse for the old section 171B(2) four-year immunity period.

There is an important procedural point too. The appeal had already failed because Sentinel had not properly run the four-year argument before the Inspector. The statutory interpretation ruling was therefore an alternative basis for dismissing the appeal rather than the sole reason for the outcome.

Neutral citation

[2026] EWHC 1122 (Admin)

Court

High Court of Justice, King's Bench Division, Planning Court

Judgment date

12th May 2026

Judge

Neil Cameron KC, sitting as a Deputy High Court Judge

Case number

AC-2025-LON-002145

What happened at 27 Pembroke Road

The property was at 27 Pembroke Road, Wembley. Brent first served an enforcement notice in January 2020 alleging a mixed use as an HMO and flats. That notice was later quashed because the Inspector found the allegation factually wrong: the premises were being used as an HMO rather than the mixed use described.

Brent served a second notice in March 2023. This time the alleged breach was a material change of use from two flats to an HMO.

Sentinel appealed. The evidence accepted by the parties was that the HMO use had begun in 2016.

The Inspector applied a ten-year immunity period

The Inspector dismissed the ground (d) appeal. He considered that HMO use fell under the ten-year rule rather than the former four-year rule for a change of use of a building to use as a single dwellinghouse.

On the accepted 2016 start date, ten years had not elapsed by the time Brent served its 2023 notice.

The Inspector also referred to the possible application of the statutory second bite provisions because Brent had taken earlier enforcement action in 2020, although he did not finally determine that issue.

The four-year argument was a new point in the High Court

Sentinel’s planning appeal documents had initially referred to the former four-year rule. But in its final written response to Brent, Sentinel acknowledged that ten years of evidence would be required for a certificate of lawfulness.

The High Court therefore treated the argument advanced in the section 289 appeal, that the four-year rule actually applied, as a new point.

Allowing that point to be run would also have required the Inspector to deal with the second bite issue and make a further judgment about whether the 2020 and 2023 notices concerned the same actual breach of planning control.

Neil Cameron KC held that the new point should not be permitted. That conclusion was sufficient by itself to dismiss Sentinel’s appeal.

The court still considered the old four-year rule

Because the statutory interpretation issue had been fully argued, the judge went on to decide it in the alternative.

The old section 171B(2) applied where there had been a breach consisting in the change of use of a building to use as a single dwellinghouse. It imposed a four-year enforcement period.

The key question was whether an HMO could fall within that wording.

An HMO can still be a dwellinghouse

The judgment carefully separates two planning concepts which are easy to blur.

An HMO can be a dwellinghouse. The court followed the earlier Brent case and the familiar Gravesham approach: where the premises provide the facilities required for day-to-day private domestic existence, an HMO may retain the planning character of a dwellinghouse.

That is also why a small Class C4 HMO can have permitted development rights which are expressed to apply to a dwellinghouse.

But that did not answer the separate question whether the HMO was being used as a single dwellinghouse for the purposes of the historic enforcement time limit.

Use as a single dwellinghouse excluded multiple occupation

The judge held that Parliament’s use of the word single was deliberately restrictive.

In this context it did not merely count how many physical buildings existed. It qualified the nature of the residential use. The phrase was contrasted with multiple occupation.

The court also considered the Parliamentary material surrounding the introduction of the predecessor provision in 1968. The minister had expressly explained that changes to multi-occupation were intended to remain outside the shorter enforcement period.

The judge therefore concluded that the historic words use as a single dwellinghouse did not include an HMO.

Class L did not determine the meaning of the older legislation

Sentinel relied on the wording of Class L, which permits certain changes between Class C3 dwellinghouses and Class C4 HMOs.

The court accepted that delegated legislation can sometimes help with interpretation, but Class L was introduced many decades after the predecessor of section 171B(2). It was not sufficiently contemporaneous to show what Parliament had intended in 1968 or 1991.

The current relationship between C3, C4 and Class L therefore should not be read backwards as though it rewrote the historic enforcement provision.

The second bite issue was left for another case

Section 171B contained a provision allowing further enforcement action where the authority had taken or purported to take earlier enforcement action in respect of the same breach within the relevant period.

Brent argued that the 2020 notice potentially gave it that second bite even if the four-year rule otherwise applied.

The Inspector had not determined whether the two notices were directed at the same actual breach. Because Sentinel’s appeal failed for other reasons, the High Court did not decide that factual and legal question either.

Sentinel should therefore not be cited as establishing that Brent’s second notice was necessarily protected by the second bite provision.

The ordinary English enforcement period is now ten years

The factual breach in Sentinel pre-dated the enforcement reforms made by the Levelling-up and Regeneration Act 2023.

In England, from 25th April 2024, the ordinary enforcement period for operational development and material changes of use became ten years, subject to transitional protection for older breaches where the former four-year period had already begun before that date.

That means the historic four-year HMO argument is now most important for older and transitional cases. For a current case, start with our enforcement time limits guide rather than assuming the pre-2024 rules still apply.

Why Sentinel still matters for lawful HMO claims

The case remains very useful when reconstructing the planning history of an HMO and deciding what period of evidence was needed under the law applying at the relevant time.

It also reinforces the distinction between three separate questions:

• whether the premises have the planning character of a dwellinghouse
• whether the use falls within Class C3, Class C4 or a sui generis HMO use
• which enforcement time limit applies to the particular breach and date

Our practical guide to proving an HMO’s status is on the Lawful HMO page.

Read the full Sentinel Estates judgment

The approved Planning Court judgment is held in the Planning Geek case law library. Gold Members can open the protected PDF below.

Sentinel Estates Case Law Page Updated: 9th September 2026