Section 57(4) TCPA 1990: Reverter Turns on the Statutory Counterfactual, Not “New Planning Unit” Extinguishment or Spatial Unity

1. Introduction

This appeal concerned the scope and proper application of section 57(4) of the Town and Country Planning Act 1990 (“TCPA 1990”), which creates a limited exception to the general rule that planning permission is required for “development”. Section 57(4) provides that where an enforcement notice is issued “in respect of any development of land”, planning permission is not required for the land to be used for the purpose for which it could lawfully have been used if that development had not been carried out.

The appellant, Titchfield Festival Theatre Limited, operated a theatre complex across three interconnected areas (A, B and C). Fareham Borough Council (“FBC”), the local planning authority, issued an enforcement notice alleging (i) an unauthorised material change of use of units B and C to theatre use and (ii) unauthorised engineering operations (excavation and creation of an underground area) beneath the land.

At the inquiry, the appellant advanced a “fallback” position: if enforcement were upheld, it said it could revert (without permission) to previously lawful uses—namely theatre use in areas A and B and storage use in area C—by reliance on s.57(4). The inspector rejected that fallback, largely by reasoning that the unlawful development had created a new planning unit that extinguished the earlier rights, and by adopting a “spatial unity” approach. The High Court upheld the inspector. The Court of Appeal allowed the appeal and ordered redetermination by a different inspector.

2. Summary of the Judgment

The Court of Appeal held that the inspector (and the High Court) fell into error by failing to apply the statutory counterfactual hypothesis mandated by s.57(4): the decision-maker must assume that the unlawful development alleged in the enforcement notice had not been carried out. On that hypothesis, the pre-breach lawful uses (theatre use for area B in conjunction with area A; storage/workshop use for area C) prevail.

The Court rejected the notion—advanced via reliance on Stone v Secretary of State for Communities and Local Government [2014] EWHC 1456—that s.57(4) is confined by a “spatial unity” requirement or defeated because the unlawful development created a new planning unit that extinguished prior rights. Such reasoning was irrelevant because the “new planning unit” arose only in the real world after the breach; s.57(4) requires the opposite inquiry.

The appeal succeeded on the ground that errors in applying s.57(4) infected both the inspector’s planning merits assessment (ground (a)) and her refusal to vary the enforcement steps (ground (f)). The matter was remitted for a fresh inquiry before a different inspector.

3. Analysis

3.1 Precedents Cited

(A) The core authority on s.57(4): Young v Secretary of State for the Environment [1983] 2 AC 662

Young was treated as the “main authority” on the interpretation of s.57(4). The House of Lords held that s.57(4) permits reverter only to the use immediately preceding the development enforced against, and only if that immediately preceding use was lawful; it does not allow a landowner to “follow the planning history” back to the last lawful use.

Crucially for this case, the Court of Appeal extracted the methodological point in Young: s.57(4) requires adoption of a specific hypothesis—assume the development alleged in the enforcement notice “had not been carried out” and ask, on that assumption, what lawful use would have continued. That hypothesis excludes importing real-world consequences of the unlawful development (such as a “new planning unit” said to have displaced prior rights).

(B) Statutory fictions and “deeming” logic: Fowler v Revenue and Customs Commissioners [2020] UKSC 22; [2020] 1 WLR 2227 and East End Dwellings Co Ltd v Finsbury Borough Council [1952] AC 109

The Court used Fowler (and Lord Asquith’s well-known formulation in East End Dwellings) to reinforce that when Parliament imposes a statutory assumption, decision-makers must not allow their reasoning to “boggle” at its necessary corollaries. Here, the inevitable corollary of assuming the unlawful development did not occur is that the pre-breach lawful uses remain the reference point.

(C) The “planning unit” tool (material change of use context): Burdle v Secretary of State for Environment [1972] 1 WLR 1207 and Johnston v Secretary of State for the Environment (1974) 28 P & CR 424

Burdle set out the familiar, non-exhaustive criteria for identifying the relevant planning unit when assessing whether a material change of use has occurred: occupation as the starting point; single main purpose with ancillary uses; mixed/composite use; and the circumstances in which physically separate areas can constitute separate planning units. Johnston reiterated that planning unit identification is a matter of fact and degree, challengeable only on Wednesbury principles.

The Court of Appeal’s key move was to distinguish the legitimate use of “planning unit” analysis in determining whether there was a breach (a material change of use) from its illegitimate deployment to defeat s.57(4). Section 57(4) does not ask whether a new planning unit has been formed by the breach; it asks what the lawful use would have been if the breach had not occurred.

(D) “Materiality” and planning purposes: East Barnet Urban District Council v British Transport Commission [1962] 2 QB 484, Westminster City Council v Great Portland Estates plc [1985] AC 661, and Barton Park Estates Limited v Secretary of State for Housing, Communities and Local Government [2022] EWCA Civ 833; [2022] PTSR 1699

These authorities were cited for general propositions: materiality focuses on the character of the use of land rather than the personal purposes of the occupier (East Barnet), and the relevant considerations are those related to planning purposes and the character of the use (Great Portland Estates; Barton Park Estates).

Their role in this appeal was contextual: the inspector’s reasoning about impacts and “character” was not the legal test for s.57(4), because s.57(4) is a statutory exception operating by counterfactual disregard, not an evaluative re-characterisation of the post-breach position.

(E) Limits of judicial supplementation of planning code: Pioneer Aggregates (UK) Limited v Secretary of State for the Environment [1985] AC 132

Pioneer Aggregates was used to emphasise that planning is a comprehensive statutory code and courts must not introduce extra-statutory principles where the statute already addresses the situation. This point was deployed to reject adding judicially-created requirements of “spatial unity” and “purposive unity” to s.57(4) in the absence of supporting statutory language.

(F) Enforcement notices must not prohibit lawful uses: Mansi v Elstree Rural District Council (1965) 16 P & CR 153 and Day and Mid-Warwickshire Motors Limited v Secretary of State for the Environment (1979) 78 LGR 27

Mansi established the principle that an enforcement notice must be framed so as not to prohibit lawful activities that are not part of the breach alleged (in Mansi, lawful ancillary sales). Day and Mid-Warwickshire Motors illustrates application of the Mansi principle to protect a reverter under s.57(4).

The Court of Appeal drew a sharp line: Mansi addresses the drafting and effect of enforcement requirements on surviving lawful rights, but it does not supply an interpretive gloss on the meaning and scope of s.57(4). In other words, Mansi may become relevant once s.57(4) is properly applied; it is not a tool to narrow or widen s.57(4) itself.

(G) The misunderstood decision: Stone v Secretary of State for Communities and Local Government [2014] EWHC 1456

The inspector and High Court treated Stone as supporting a narrow “spatial unity” conception of s.57(4). The Court of Appeal rejected that reading.

Properly understood, Stone turned on its “unusual facts”: the only asserted lawful fallback was a mixed use authorised by a planning permission over a larger area (area D) that necessarily included a residential component; but the enforcement notice (as varied) excluded the residential part. The mixed-use permission could not lawfully be exercised on the truncated area remaining within the enforcement notice.

The Court of Appeal therefore treated Stone as illustrating a straightforward proposition—s.57(4) applies to the land within the enforcement notice as drawn— but not as laying down a further rule that s.57(4) is confined to cases of single spatial or purposive unity, or defeated by a post-breach “new planning unit” analysis.

(H) “New planning unit” / “new chapter” authorities (extinguishment/incompatibility line): Prossor v Minister of Housing and Local Government (1968) 67 LGR 109, Petticoat Lane Rentals Limited v Secretary of State for the Environment [1971]1 WLR 1112, Newbury District Council v Secretary of State for the Environment [1981] AC 578, Jennings Motors Limited v Secretary of State for the Environment [1982] QB 541, and South Staffordshire District Council v Secretary of State for the Environment (1988) 55 P & CR 258

These cases address when implementing a planning permission (or undertaking development) can be inconsistent with the continuation of earlier established use rights, sometimes described as opening a “new chapter” in planning history or creating a “new planning unit”.

The Court of Appeal used them to clarify terminology and avoid conceptual confusion: “Planning unit” (the Burdle tool) helps identify the unit for assessing material change of use. By contrast, “new planning unit/new chapter” addresses a different question: whether implementation of a permission or development is incompatible with, and thus extinguishes, earlier rights.

The Court held that this “new chapter” line was a distraction in the present case because the central question was s.57(4), which requires ignoring the unlawful development. Whether the unlawful works would, in the real world, be said to have opened a new chapter is “beside the point” when applying the statutory hypothesis.

(I) Permissions interacting (by analogy): Pilkington v Secretary of State for the Environment [1973] 1 WLR 1527 and Hillside Parks Limited v Snowdonia National Park Authority [2022] 1 WLR 5077

These were mentioned by analogy (in a footnote) to the idea of incompatibility between planning rights. They did not drive the ratio, but underscore the Court’s theme: extinguishment or non-reliance issues arise from incompatibility analyses in their proper doctrinal setting, not as an overlay on s.57(4)’s counterfactual exercise.

3.2 Legal Reasoning

(A) The statutory architecture: s.57(4) as a narrow, conditional exception

The Court emphasised that Parliament already limited s.57(4) in specific ways (notably: it only operates where an enforcement notice is issued; it concerns “development” rather than breach of condition; it authorises reverter of use only, not operational development; and it operates within the land to which the enforcement notice applies). Those express limitations made it illegitimate to graft on further judge-made limitations (such as “spatial unity” or “purposive unity”) without textual support.

(B) The correct method: five-step application of the counterfactual

Holgate LJ distilled the decision-maker’s task into a structured approach:

1. Identify the development alleged by the enforcement notice to be a breach on the land to which the notice applies.
2. Identify the use of that land immediately before that breach.
3. Assume the breach has not occurred (the statutory disregard).
4. On that assumption, ask whether the immediately preceding use was lawful.
5. If it was lawful, planning permission is not required to revert to that use.

Applying that method, it was an error to reason that because the unlawful development created a new planning unit and a material change of use, the pre-existing rights were “lost”. Those were real-world consequences of the very breach that must be assumed away.

(C) Rejection of “spatial unity” and “purposive unity” as implied requirements

The Court rejected the Secretary of State’s attempt to confine s.57(4) to cases where, before the breach, the enforcement notice land formed a single spatial unit with a common use (or a mixed use within one unit). Nothing in the language of s.57(4) supports such a limitation. In particular:

• The statute is capable of dealing with multiple “uses/purposes” (singular includes plural under s.6 Interpretation Act 1978).
• The statutory question is simply what lawful uses would have continued on the enforcement notice land if the breach had not occurred—regardless of whether those uses were previously distributed across more than one planning unit.

(D) The inspector’s and High Court’s legal error: importing post-breach concepts into the counterfactual

Both the inspector and the High Court treated “new planning unit/extinguishment” as determinative against the fallback. The Court held this was legally irrelevant to s.57(4), because it answered the wrong question (what happened in the real world after the breach) rather than the statutory hypothesis (what would have happened if the breach had not been carried out).

(E) Remedy: remittal for redetermination

Because s.57(4) was central to the inspector’s analysis of both (i) the planning balance under ground (a) and (ii) whether the steps required exceeded what was necessary under ground (f), the errors tainted the decision as a whole. The case was remitted for redetermination at a fresh public inquiry before a different inspector.

3.3 Impact

• Re-centres s.57(4) on the statutory counterfactual: inspectors and courts must apply the “assume the breach did not occur” hypothesis rigorously; reasoning based on the consequences of the breach (e.g. creation of a new planning unit) will be vulnerable to challenge.
• Rejects implied “spatial unity” limits: where an enforcement notice covers land that, immediately before the breach, had different lawful uses in different parts, s.57(4) can in principle permit reverter to those different lawful uses across the notice land (subject to the notice’s defined land and the lawfulness of those uses).
• Narrows the practical reach of Stone: the decision discourages reliance on Stone as a general interpretive authority on s.57(4), confining it to cases where (often because of mixed-use permissions or the way the notice is drawn/varied) the claimed lawful use cannot be exercised on the enforcement notice land.
• Enforcement strategy consequences for LPAs: since s.57(4) only operates if an enforcement notice is issued, the Court’s reading reinforces that LPAs retain a gatekeeping function: they may decide not to issue a notice if reverter to lawful prior uses would be worse than the unauthorised use—but once they do issue, s.57(4)’s counterfactual must be applied.
• Clarifies doctrine and terminology: the judgment draws a firmer boundary between (i) “planning unit” for identifying material change of use and (ii) “new chapter/new planning unit” for incompatibility-based extinguishment, reducing conceptual slippage in enforcement appeals.

4. Complex Concepts Simplified

• Development / material change of use: “Development” includes certain operations and “material” changes in use. A change is “material” if it matters for planning purposes (e.g. traffic, noise, amenity impacts).
• Enforcement notice: a formal notice requiring steps to remedy an alleged breach of planning control (e.g. stop a use; remove works; restore land). It can be appealed on statutory grounds (including ground (a) deemed permission; ground (f) excessive steps; ground (g) time for compliance).
• Planning unit: a fact-based way to define the relevant unit of land/buildings for assessing use and whether a material change has occurred. It often follows occupation and how uses are arranged (single main use, mixed use, or physically separate uses).
• Section 57(4) “reverter”: if an enforcement notice is issued for development, you may not need permission to go back to the use that would have existed if the unlawful development had not happened—provided that earlier use was lawful.
• Statutory counterfactual (deeming): the law sometimes instructs decision-makers to assume a hypothetical world. Here, you must assume the unlawful development never happened and then decide what lawful use would have continued.
• Mansi principle: an enforcement notice should not be drafted so broadly that it stops lawful activities not actually part of the breach. It is about the notice’s effect, not about rewriting the meaning of s.57(4).
• “New chapter in planning history” / “new planning unit” (extinguishment): shorthand for situations where implementing development (often under a permission) is incompatible with continuing earlier rights. This is a different inquiry from s.57(4)’s counterfactual reverter analysis.

5. Conclusion

The Court of Appeal established and reinforced a clear rule: the application of s.57(4) is governed by its statutory counterfactual. Decision-makers must assume the unlawful development alleged in the enforcement notice was not carried out, and then determine whether the immediately preceding use of the enforcement notice land was lawful; if so, reverter requires no planning permission.

In doing so, the Court rejected attempts to narrow s.57(4) by importing “spatial unity” or “purposive unity” requirements, and condemned the misuse of “new planning unit/new chapter” reasoning to defeat reverter—because that reasoning is founded on the real-world effects of the breach that s.57(4) commands decision-makers to disregard.

The judgment is significant both for enforcement appeals (where fallback positions frequently matter to the planning balance and to the proportionality of enforcement steps) and for doctrinal clarity: it confines Stone to its facts, reasserts Young as the controlling authority, and insists on disciplined adherence to the statutory hypothesis at the heart of s.57(4).