Proprietary Estoppel

September 4, 2025

Proprietary Estoppel in English Law: A Comprehensive Overview

Proprietary estoppel is an equitable doctrine that prevents a person from denying a promise relating to rights in property when another has relied on that promise to their detriment. In practical terms, it can create rights over land or property in favour of a claimant where enforcing the strict legal position would be unjust. Unlike other forms of estoppel, proprietary estoppel can act as a sword, a cause of action, and not merely a shield, thus allowing a claimant to enforce a broken promise of property, not just defend against claims. This article provides a comprehensive look at proprietary estoppel in English law, covering its historical development, the key principles and requirements for a claim, a comparison with promissory estoppel, leading case law, and current trends or emerging issues in this area.

Historical Background and Development

Victorian Origins: The roots of proprietary estoppel trace back to 19th-century equity. Early cases like Dillwyn v Llewelyn (1862) 4 De G F & J 517; 45 ER 1285 set the tone: in that case, a father assured his son he would have a piece of land and even gave written notice, leading the son to build a house on it. When no formal deed was completed, the court nevertheless enforced the promise and deemed the son to have acquired the house in equity. Ramsden v Dyson (1866) LR 1 HL 129 articulated the principle that if an owner stood by while another spent money on the land in the expectation of a right, it would be unconscionable to later deny that right.

The Five Probanda: In Willmott v Barber (1880) 15 Ch D 96, Fry J set out a strict five part test for proprietary estoppel, requiring the claimant to show that they laboured under a mistake as to their rights, did something in reliance, and that the landowner knew of their true rights and the claimant’s mistake yet encouraged the reliance. This was a relatively rigid framework aimed at pinpointing when it would be inequitable for an owner to insist on their strict legal title. However, the five probanda approach proved too strict and was gradually relaxed over time.

Modern Flexible Approach: By the late 20th century, courts had shifted to a more flexible, fairness-based approach. A case marking this shift was Taylors Fashions Ltd v Liverpool Victoria Trustees Co Ltd [1982] QB 133 (Ch), where Oliver J rejected hard-and fast rules and emphasised that unconscionability is the guiding principle. Rather than checking off five technical factors, the court began asking whether, in the circumstances as a whole, it would be unconscionable for the promisor to renege on their assurance. Subsequent cases adopted this modern approach: the essential ingredients crystallised into (1) a clear promise or assurance of rights in property, (2) reasonable reliance on that promise, and (3) detriment suffered by the claimant as a result, with all elements viewed in the round under an umbrella of preventing unconscionable conduct (Thorner v Major [2009] UKHL 18, [2009] 1 WLR 776 (HL); Gillett v Holt [2001] Ch 210 (CA)).

In other words, by the 21st century proprietary estoppel had evolved from a narrow defensive doctrine into a broad principle empowering courts to do equity in property cases. This evolution laid the groundwork for today’s more claimant-friendly use of proprietary estoppel as a means of enforcing informal promises of property.

Key Legal Principles and Requirements

To succeed in a proprietary estoppel claim, a claimant must establish an equity in their favour by proving certain key requirements. These requirements, often overlapping, are examined collectively rather than as isolated hurdles. The modern essentials can be summarised as follows:

Assurance or Promise: There must have been a clear promise or assurance made to the claimant that they either have or will have some right or interest in the property. This assurance can be explicit, for example, “One day, all this will be yours”, or inferred from conduct, so long as a reasonable person in the claimant’s position would take it as a serious commitment. It need not spell out every detail, but vague or casual remarks will not usually suffice; the courts look for enough certainty to ground an expectation. For example, in one case a landowner’s comments were too equivocal and lacked any written confirmation, so the claimant could not prove a genuine promise of inheritance.

Reliance: The claimant must have relied on the promise in such a way that they changed their position because of it. The reliance has to be reasonable and caused by the assurance; the question is whether the promise influenced the claimant’s decisions or actions. Often this is demonstrated by the claimant making life choices they would not have made but for the promise. For instance, claimants frequently devote years of work or forgo other opportunities in reliance on an expected inheritance of property, for example by working for low pay on the family farm rather than pursuing a different career, because they were led to believe the farm would be theirs. Importantly, once an assurance is shown, the burden may shift to the defending party to prove the claimant did not rely to their detriment, but in practice, reliance and detriment often go hand in hand.

Detriment: The claimant must have suffered a detriment as a result of their reliance. Detriment is interpreted broadly; it is not limited to direct financial loss. Classic examples include expending money or labour on the property, such as paying for improvements or building on the land, or giving up something valuable, like an alternative job, home, or opportunity, because of the promise. The courts will compare what the claimant gave up or endured on the strength of the promise with what they stood to gain. For example, working for decades for little pay in expectation of inheriting property is a detriment, even if the claimant received some benefits along the way. Recent rulings have stressed that detriment can be non-financial; intangible sacrifices of life choices and opportunities can count just as much as out-of-pocket expenses. The key is that the claimant’s situation is worse, or would be if the promise is not kept, than if the promise had never been made.

Unconscionability: Finally, and fundamentally, the claimant must show that, in light of the above, it would be unconscionable, meaning inequitable or unjust, for the promisor to go back on their word. Unconscionability is the moral glue of proprietary estoppel; the court considers all the circumstances and asks if it would be dishonest or oppressive to allow the promisor to deny the assurance after inducing the claimant’s reliance and detriment. This is not a separate element so much as an overall assessment that ties the strands together. Even if the technical elements of promise, reliance, and detriment are present, the court will only intervene if denying the claim would be, in Lord Walker’s words, “shocking to the conscience of the court.” Conversely, if the outcome does not strike the court as unconscionable, an estoppel claim will fail. The doctrine is not a mechanism to enforce casual promises or family aspirations without more.

When these elements are established and an equity arises in the claimant’s favour, the court’s task is to satisfy that equity by awarding an appropriate remedy. Notably, proprietary estoppel is an equitable doctrine, so the court has flexibility in how to do justice. The usual expectation is that the promise will be honoured to the extent necessary to avoid unfairness. In many cases, this means the claimant is given the very property right they were promised, or something close to it, if that is required to meet the equity. However, the remedy is not automatic or all or nothing; it is fashioned based on proportionality. The goal is to prevent the promisor from unconscionably disappointing the claimant’s expectation. In summary, the doctrine demands clarity of promise, reasonable reliance by the promisee, detriment incurred, and overall inequity (unconscionability) before the court will step in to effectively estop the promisor from resiling on their word.

Leading Case Law in Proprietary Estoppel

Inwards v Baker [1965] 2 QB 29 (CA): A classic family case demonstrating the doctrine. A father encouraged his son to build a bungalow on the father’s land, assuring him he could live there as long as he liked. The son built the house at his own expense and lived there for decades. After the father died, his estate tried to evict the son. The Court of Appeal held that the son had an equity and could remain for life. Lord Denning MR explained that when someone spends money on another’s land with that landowner’s encouragement, in the expectation of being allowed to stay, equity will intervene to prevent that expectation from being defeated. The son’s expenditure and reliance raised an equity which the court satisfied by granting him a licence to live in the bungalow for his lifetime.

Crabb v Arun District Council [1976] Ch 179 (CA): A leading case often cited for the idea of the “minimum equity to do justice.” Mr Crabb was assured by the council that he would have a right of access (a roadway) to his land if he sold part of it. Relying on this, he sold part of his land, leaving his remaining plot landlocked except for the promised access point. When the council later tried to deny him the access or attempted to charge a hefty fee, the court held that an estoppel arose. It would be unconscionable to let the council renege after Crabb had irreversibly arranged his affairs by selling land on the strength of their assurance. He was granted a right of way without payment. As Scarman LJ put it, equity will award the minimum relief necessary to do justice. In this case, that meant giving Mr Crabb the easement he was promised.

Pascoe v Turner [1979] 1 WLR 431 (CA): An example of estoppel in a domestic cohabitation context. Mr Pascoe told Ms Turner, his long time partner, that “the house is yours,” leading her to believe she owned the house. She then spent her own money extensively improving and decorating the property. When the relationship broke down, Mr Pascoe tried to reclaim the house. The court found a clear assurance and detrimental reliance. Ms Turner had indeed acted on the promise to her detriment. To satisfy the equity, the court transferred the house to Ms Turner outright, essentially enforcing the promise literally. This case is noted for the relatively high level of relief (the entire property) given that her detriment, while significant in proportion to her means, was much less than the house’s full value. The court felt that nothing short of giving her the house would do justice, demonstrating the willingness of the court to compel an actual transfer of ownership as a remedy in appropriate cases.

Gillett v Holt [2001] Ch 210 (CA); [2000] 3 WLR 815: A significant modern case reinforcing that the elements of proprietary estoppel are fluid and interrelated. Mr Gillett worked on Mr Holt’s farm from the age of 15 for low wages, after Holt repeatedly assured him that “One day, this will all be yours.” Over several decades, Gillett was named as a beneficiary in Holt’s wills. A falling out led Holt to cut Gillett out and dismiss him. The Court of Appeal held that repeated assurances over the years can cumulatively amount to a clear promise, and Gillett’s life changing reliance (tying his entire career to the farm) and detriment were evident. Crucially, the court stressed that the doctrine should not be broken into isolated compartments: assurance, reliance, and detriment influence each other, and unconscionability permeates the analysis. Gillett was awarded the freehold of the farmhouse and a significant sum of money as expectation-based relief. The case stands for the proposition that once the promisee has paid a heavy price in reliance on a promise, the promisor cannot lightly withdraw that promise.

Jennings v Rice [2002] EWCA Civ 159; [2003] 1 P & CR 100 (CA): A case famous for its guidance on proportionality in remedies. Mr Jennings worked as a gardener and caretaker for an elderly woman, Mrs Royle, for little pay, based on her vague assurances. When she died intestate, he claimed the entire estate, worth around £1.3 million at the time, based on those promises. The Court of Appeal agreed that an estoppel had arisen: there was an assurance and he had devoted years of loyal service, evidencing reliance and detriment. However, the remedy was not the full value of the estate. Lord Justice Robert Walker emphasised that the court’s role is to avoid an unconscionable result and that the remedy must be proportionate to the detriment suffered. Here, awarding the entire estate would have been extravagant compared to Mr Jennings’ detriment. Instead, the court awarded £200,000, reasoning that this sum fairly compensated his sacrifices and was sufficient to avoid injustice.

Cobbe v Yeoman’s Row Management Ltd [2008] UKHL 55; [2008] 1 WLR 1752: A House of Lords decision highlighting the limits of proprietary estoppel, especially in commercial contexts. Cobbe, an experienced property developer, had an oral “in principle” agreement with a landowner,Yeoman’s Row Management, to buy and develop certain property, but no formal contract was signed. In fact, both parties knew that a legally binding contract would be needed. Cobbe went ahead and spent time and money obtaining planning permission; then the owner tried to renegotiate for a higher price. Cobbe claimed an estoppel to enforce the original deal. The House of Lords rejected the claim. They found that no sufficiently clear and unequivocal promise of an interest in the land had been made, both sides were negotiating and knew the deal wasn’t final. Moreover, in a commercial arm’s length transaction, the parties expect to be bound only when a formal contract is signed. It was not unconscionable for the owner to insist on a signed contract. This also intersects with the Statute of Frauds requirement of written evidence for land contracts. Lord Scott cautioned that proprietary estoppel should not be allowed to become an undemanding alternative to a proper contract where parties deliberately left matters open. Cobbe is thus a warning that estoppel will not lightly trump formal requirements in a commercial deal, and that a claimant’s knowledge and experience matter. Mr Cobbe knew the risks and the need for a written contract, so his reliance was deemed unreasonable in law. This case introduced some tension in the doctrine, seemingly requiring a higher standard of clarity, and perhaps formality, in commercial settings as opposed to familial or informal contexts.

Thorner v Major [2009] UKHL 18; [2009] 1 WLR 776 (HL): Decided soon after Cobbe, this House of Lords case swung the pendulum back in favour of a more flexible approach in domestic/family contexts. David Thorner worked unpaid on his cousin Peter’s farm for 30 years, on the unspoken understanding that he would inherit it. Peter never said so explicitly, but over the years he made oblique remarks, for example, he once handed David an insurance bonus notice and said it was for his “death duties”, which David understood as confirming the promise that the farm would be left to him. Peter died intestate, after destroying a will in David’s favour during a dispute with another relative. The question was whether the assurance was sufficiently clear to found an estoppel, given it was never spelt out. The House of Lords unanimously upheld David’s claim. Importantly, the Law Lords held that, in context, Peter’s conduct did convey a clear enough assurance. Even if it was indirect and “allusive,” a reasonable person in David’s position would have taken it as a firm commitment that he would inherit. Indeed, in Thorner v Major [2009] UKHL 18, Lord Hoffmann stated that clarity is assessed in context: what might be fatally vague in a business deal can be sufficiently clear in a family farm setting where people often rely on understandings built over years. Thorner v Major thus affirmed that context is critical and that courts are prepared to infer a promise from conduct in long term domestic or family arrangements. It also contrasts with Cobbe, indicating that family and farm cases are treated more benevolently, and less formally, than commercial cases. The estoppel was satisfied by essentially awarding David the farm, or its substantial equivalent, fulfilling the expectation that had arisen.

Guest v Guest [2022] UKSC 27; [2024] AC 833: A very recent case, notably the first time the UK Supreme Court squarely addressed proprietary estoppel remedies. Like many others, this case involved a family farm. The parents, David and Josephine Guest, had promised their eldest son, Andrew, that he would inherit a working share of the farm business and land, enough to continue farming, along with his brother, while providing some cash to their sister. Relying on this, Andrew worked on the farm for over 30 years for low wages and lived in tied accommodation. After a severe family rift, the parents rewrote their wills to effectively disinherit Andrew, and they evicted him. Andrew sued while his parents were still alive. The trial court and the Court of Appeal upheld his estoppel claim and fashioned a remedy: the parents were ordered to pay Andrew a lump sum, around £1.3 million, representing the present value of his expected inheritance, effectively a “clean break” so he could buy his own farm. The parents appealed on the issue of the remedy, arguing that the court should award only minimal compensation for his detriment, rather than the full expectation value of the promise.

The Supreme Court, in a split decision (3–2), confirmed that the starting point for a remedy in proprietary estoppel is the claimant’s expectation, not merely their detriment. Lord Briggs (for the majority) reasoned that the purpose of the doctrine is to prevent or undo unconscionability, which often means holding the promisor to their promise unless doing so would be out of proportion to the detriment suffered. He rejected a strict “detriment-based” approach. However, the Court also acknowledged that giving the claimant exactly what was promised may in some cases overshoot what is necessary to avoid injustice, particularly if circumstances have changed or if the promise was conditional on a future event like the promisor’s death. In Guest, because Andrew was receiving his inheritance early, during the parents’ lifetime rather than after their deaths, the majority adjusted the remedy to be fair to both sides. The parents were given a choice: either (a) give Andrew a share of the farm and business as promised, but hold it on trust until their deaths (so the parents could still draw income for life), or (b) pay him an immediate lump sum of compensation, discounted to reflect the early receipt. This choice was intended to satisfy the equity while recognising the parents’ position. The parents ultimately opted to make the financial payment, which will amount to substantially less than the farm’s full value, accounting for Andrew receiving it sooner than expected. The minority (Lord Leggatt and Lord Stephens) disagreed, preferring a purely compensatory award equal to Andrew’s net detriment, which they calculated to be around £610,000.

English law now leans towards an expectation based remedy in estoppel (i.e. fulfilling the promise), but with flexibility. Courts should start by asking what the claimant was promised, then consider whether granting that in full would itself produce an unjust result. For example, it may result in an overcompensation relative to the promisee’s detriment or impose an undue hardship on the promisor, as discussed in Crabb v Arun District Council [1976] Ch 179 and Jennings v Rice [2003] EWCA Civ 159. If full enforcement would be excessive, the remedy can be trimmed down, a concept sometimes expressed as the “minimum equity to do justice,” revived from Crabb v Arun. This case also illustrates the willingness of courts to resolve such disputes even during a promisor’s lifetime, so as not to prolong uncertainty. Importantly, Guest v Guest confirms that proprietary estoppel can compel a positive outcome, whether a transfer of property or a payment, and is not confined to merely withholding enforcement of rights, reinforcing its distinctiveness from promissory estoppel.

Recent Trends and Emerging Issues

Rise of Intra-Family Farm Disputes: A striking number of modern estoppel cases involve family farms or small family businesses. As land values have increased, so too have the stakes, and courts have seen more children suing parents or siblings over broken promises of inheriting farms or land. Traditionally, such claims arose after the parent’s death, when the will revealed an unpleasant surprise, but there is a growing trend of lifetime claims where the promised heir brings the case while the elder generation is still alive. This reflects an unfortunate reality that many farming families still rely on handshake promises instead of formal succession planning, leading to bitter litigation later.

Emphasis on Clear Assurances: While the doctrine is flexible, courts in recent cases have placed renewed emphasis on the need for a sufficiently clear and unequivocal assurance as the foundation of an estoppel. Where claimants cannot prove a definite promise or assurance, their claims fail, even if they feel wronged by the situation. Two High Court cases in 2023 (Gladstone v White and Mate v Mate) illustrate this point. In Gladstone v White, a family friend claimed an elderly landowner had promised her a valuable country house, but the court found that his words and conduct fell far short of a promise of ownership; he may have intended to involve her in managing the estate, but never clearly said she would inherit the house (Gladstone v White [2023] EWHC 329 (Ch)). Her claim was rejected for lack of a concrete assurance. Similarly, in Mate v Mate, a daughter’s claim that her mother promised her a share of farm sale proceeds failed because the alleged promises were too vague and not proven to the court’s satisfaction (Mate v Mate [2023] EWHC 238 (Ch)). These cases signal that, even in a family setting, a claimant must pinpoint a promise with reasonable clarity and not just hold a subjective expectation. Courts are unwilling to impose obligations on property owners based on casual remarks or hopeful interpretations.

Reaffirmation of Detriment (Including Non-Financial): Recent judgments have also clarified that detriment is assessed broadly, and any countervailing benefits arguments will be scrutinised. For example, in Winter v Winter [2024] EWCA Civ 699, the Court of Appeal held that two sons who received certain benefits, such as shares worth £2 million, still suffered a detriment from devoting their working life to the family business for low pay. The court disagreed with the argument that those benefits offset any detriment: devoting one’s working life on the strength of a promise can still be a detriment despite receiving some financial benefits, especially if those benefits were inherent in the arrangement, not a gratuitous gift. In reaching this conclusion, the court in Winter cited Spencer v Spencer [2023] EWHC 2050 (Ch) approvingly, emphasising that opportunity cost and life decisions forgone count as detriment. In short, judges are looking at the overall position of the promisee: did they end up materially worse off, or locked into a disadvantageous situation, because they trusted the promise? If so, detriment is present, even if on paper they earned some money or received some benefits along the way. This approach ensures that the focus remains on fairness and not just a balance-sheet comparison.

Remedial Flexibility after Guest v Guest: The Supreme Court’s decision in Guest v Guest has provided clarity that the remedy in proprietary estoppel should normally aim to satisfy the claimant’s expectation, what they were promised, subject to the important limitation of proportionality. The majority explicitly rejected the idea that the goal is only to compensate for detriment (Guest v Guest [2022] UKSC 27; Jennings v Rice [2003] EWCA Civ 159). Instead, the two-stage approach is: first, establish if an equity arises, was the broken promise unconscionable given the reliance and detriment?) second, craft the remedy starting from the assumption that the promise should be kept, but then reduce it if full enforcement would be over-generous or otherwise unjust. Early indications from subsequent cases are that lower courts are indeed following the guidance from Guest. For example, judges now carefully consider whether to discount an award if the promise is being accelerated, as in Guest itself where the inheritance was effectively received early, or if the claimant’s expectation was out of proportion to their detriment. The Guest ruling also, interestingly, allowed giving the promisor a choice of remedy (to transfer the property or to pay money) (Guest v Guest [2022] UKSC 27). This approach might be used in future cases to give some agency to the party who has to satisfy the equity.

High Litigation Costs and Family Strain: A practical issue that has become apparent is the cost, both financial and emotional, of proprietary estoppel litigation. These cases often require detailed factual inquiries into decades of family history, multiple witnesses, sometimes elderly, and expert valuations of property and businesses. The process can be protracted and expensive, which puts pressure on families and may dissipate the very assets in dispute. The personal nature of these claims, often pitting close relatives against each other, also means that litigation can cause deep emotional rifts and lasting trauma within families.

Calls for Reform: Given the above concerns, there have been some academic and law reform discussions about whether the law should provide a more straightforward mechanism for situations like broken inheritance promises. One idea floated is a statutory scheme to enforce oral testamentary promises, as exists in some countries, which could take many of these family cases out of the realm of estoppel litigation. For instance, New Zealand’s Law Reform (Testamentary Promises) Act 1949 allows certain claims based on promises of inheritance. If, for example, English law had an inheritance promises act enabling a claim by someone promised an inheritance, it might simplify matters compared to the broad, fact intensive estoppel route. However, no such legislation exists yet in England and Wales. For now, proprietary estoppel, and to some extent, claims for family provision under the Inheritance (Provision for Family and Dependants) Act 1975, remain the primary tools available. It will be interesting to watch whether the courts or Parliament move to refine this area further. For the moment, the flexibility of proprietary estoppel is both its strength and its challenge: it allows tailored justice in individual cases, but with that comes a measure of unpredictability.

Conclusion

Proprietary estoppel has matured into an important doctrine in English property law, functioning as a safeguard against injustice in situations where formal legal rights fall short of fairness. Its historical journey from a narrow rule to a broad equitable principle reflects the legal system’s attempt to balance the need for certainty in property transactions with the need to prevent outright unfairness. For clients and practitioners, understanding proprietary estoppel is vital whenever promises about property are made without the paperwork to back them up. Simple moral words and assurances in the context of land carry weight, and if you lead someone to reasonably rely on your word, the law may bind you to it. From a practical standpoint, the best way to avoid the uncertainty of a proprietary estoppel claim is for parties to either formalise their agreements or at least keep communications clear. Land and inheritance are high value matters that should not be left to ambiguity. Where that advice comes too late and a dispute has already arisen, the doctrine of proprietary estoppel stands as a potent, if complex, avenue for relief. It exemplifies the enduring power of equity in English law to step in, when conscience demands, and insist that promises be kept.