The Mansi principle and preserving a lawful use
The Mansi principle stops an enforcement notice removing pre-existing lawful use rights. It has to be pleaded with the proviso drafted and the evidence proved.
An enforcement notice must not be drafted so as to stop a use that was lawful before the breach happened. That is the Mansi principle, taken from Mansi v Elstree Rural District Council, and in practice it means an inspector will vary an over-wide notice by adding a proviso preserving the underlying lawful use. For a landlord with a building that has had several uses over forty years, the proviso can be worth more than winning the appeal outright.
The principle is pleaded, not assumed. Inspectors add a saving where the appellant has identified the lawful use and proved it. Where the appeal says only that the notice is too wide, without saying what use should be preserved and on what evidence, nothing is saved.
Where the principle comes from
The case concerned land used for the sale of produce as an ancillary activity, where the enforcement notice required the use of the land for retail sales to stop altogether. The court held that the notice went too far, because it would have prevented a use that was lawful independently of the breach.
The reasoning sits comfortably with the statute. Section 173(4) of the Town and Country Planning Act 1990 limits the purposes for which steps may be required to remedying the breach or remedying any injury to amenity caused by it. A requirement that also extinguishes pre-existing rights goes beyond both purposes.
Section 176(1) then supplies the remedy on appeal, allowing the inspector to correct or vary the notice provided no injustice results. A Mansi saving is a variation of the notice's requirements, not a finding that the breach did not occur.
Why a notice must not require more than remedying the breach
Councils draft notices broadly because broad notices are easier to enforce. A requirement to cease the use of the land for the storage of vehicles is simpler to police than one that permits storage of up to a stated number in a defined area.
The cost of that simplicity falls on the owner. Where a yard has a lawful use for builder's storage established in the 1980s, and the breach is an intensification into vehicle dismantling, a notice requiring all storage to cease removes a right the owner has held for decades.
| Notice requirement | Problem |
|---|---|
| Cease the use of the land for any commercial purpose | Extinguishes any lawful commercial use entirely |
| Remove all hardstanding | Removes surfacing that may be lawful or immune |
| Cease the use of the building for storage | Catches lawful storage as well as the unauthorised intensification |
| Restore the land to its condition before the breach | Workable only if that condition is defined |
Over-wide drafting is common rather than malicious. Point it out precisely and most inspectors will deal with it.
Identifying the underlying lawful use
Before pleading anything, settle what the lawful use actually is. Three possibilities, and they lead to different arguments.
A use authorised by an express planning permission, which the decision notice and conditions define. A use that is lawful because it became immune from enforcement through the passage of time, which requires evidence of continuity over the relevant period and attention to the enforcement time limits, including the changes made by the Levelling-up and Regeneration Act 2023 and whether they are in force for your facts. Or a use lawful because it predates planning control or has the benefit of a certificate.
Describe it with precision, in the terms a condition would use: the activity, the area it occupies, the intensity, the hours and any plant involved. A proviso can only preserve a use that can be stated clearly enough to be enforced against.
Two limits are worth knowing. Where the lawful use is trivial in scale, the principle may add nothing in practice. And where the earlier use has been abandoned, or has been superseded because the breach created a different planning unit, there may be no surviving right to preserve. Abandonment turns on the physical condition of the land, the period of non-use, any intervening use and the owner's intentions, and it is argued on facts rather than asserted.
Evidence of the pre-existing use
The documents that work are third-party records with dates on them.
- Rating list entries and rates demands showing the description of the premises and the effective dates
- Leases and tenancy agreements identifying the permitted use and the demised area
- Invoices, delivery notes and trading records tied to the activity
- Dated photographs, including aerial photography held by commercial and public archives
- Planning history: permissions, approvals of details, certificates and earlier enforcement files
- Statutory declarations from people with first-hand knowledge, supported by documents rather than standing alone
Build a chronology. Gaps matter more than volume, because a council will point at any period without evidence and argue discontinuity. Where the history is incomplete, say so and explain why the remaining material still establishes the use.
Asking the inspector to vary the steps
Ground (f) under section 174(2) is the usual vehicle. It argues that the steps required exceed what is necessary to remedy the breach or any injury to amenity, and it invites the inspector to substitute lesser requirements.
Plead it with the words you want. Set out the proviso you are asking for, in the form you would accept it, so the inspector has a drafting option in front of them. Something along the lines that nothing in the notice shall prevent the use of the land for the storage of building materials within the area hatched on the attached plan, that use having been lawful before the matters alleged occurred.
Then explain, briefly, why the proviso does not undermine the notice. Inspectors are reluctant to add savings that would make a notice unenforceable, so show that the preserved use is capable of being distinguished on the ground from the breach.
Ground (g) on the compliance period usually runs alongside it. Where a mixed use has to be unwound to its lawful component, the practical steps take time, and a programme with quotations supports a longer period. The structure of these findings in a decision is explained in how to read a planning appeal decision letter.
Where a certificate application is the better route
A Mansi saving is defensive. It protects what you have within an enforcement notice that otherwise stands against you. A certificate of lawful existing use or development under section 191 of the 1990 Act is positive: the council certifies what is lawful, and the certificate is conclusive for the purposes it covers.
For a landlord the difference is commercial. A certificate is a document a lender, a purchaser and a valuer can read. A proviso buried in the requirements of an enforcement notice, varied on appeal, takes explaining to all three.
So where the evidence is strong, consider applying for a certificate in parallel with the appeal rather than relying on the saving alone. Where the evidence is thin, the appeal ground is the less costly route and the proviso may be all that is realistically available. A judgment call, and one worth taking early, because the certificate application has a fee and a timetable of its own.
Drafting the appeal ground precisely
- State the lawful use in terms capable of enforcement: activity, area, intensity, hours
- Identify the legal basis for it: permission, immunity through time, or a certificate
- Attach the evidence chronologically, with a one-page schedule indexing it
- Plead ground (f) and set out the exact proviso you seek
- Explain how the preserved use is distinguishable from the breach on the ground
- Plead ground (g) with a programme if unwinding the breach takes time
- Keep any ground (a) case separate and consistent with the rest
Consistency is the point practitioners most often miss. A ground (a) case arguing that the unauthorised use is acceptable in planning terms, sitting next to a ground (f) case arguing that only the lawful use should survive, needs careful handling so the two do not contradict each other. Where the council reframes its position during the appeal, the response is set out in appeals where the council changes its case.
Any supporting planning case should be written to the same discipline, and the Planning Statement is the place to set the site history out in full. The report index lists the other documents an appeal of this kind may need.
This is general guidance, not legal advice; check the position with your local planning authority or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
What is the Mansi principle?
It is the principle, from Mansi v Elstree Rural District Council, that an enforcement notice must not be framed so as to prevent a use that was lawful before the breach. On appeal an inspector can vary the notice to add a proviso preserving that use, using the power to correct or vary under section 176 of the Town and Country Planning Act 1990.
Which appeal ground do I use?
Ground (f) under section 174(2), which argues that the steps required exceed what is necessary to remedy the breach or any injury to amenity. Set out the exact proviso you are asking for, so the inspector has drafting in front of them, and explain why the preserved use can be distinguished from the breach on the ground.
Does the principle always apply?
No. Where the lawful use is trivial in scale, a proviso may add nothing. Where the earlier use has been abandoned, or has been superseded because the breach created a different planning unit, there may be no surviving right to preserve. Abandonment is argued on the facts, including the period of non-use and the condition of the land.
What evidence proves a pre-existing lawful use?
Third-party records with dates. Rating list entries and rates demands, leases identifying the permitted use and demised area, invoices and trading records, dated and aerial photographs, and the planning history. Statutory declarations help where they are supported by documents rather than standing alone.
Is a certificate better than a Mansi saving?
Commercially, often yes. A certificate under section 191 is a positive document that a lender, purchaser or valuer can read, and it is conclusive for the purposes it covers. A proviso varied into an enforcement notice protects the use but takes explaining. Where evidence is strong, consider applying for a certificate alongside the appeal.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.