Unkept Promises: The Evolving Landscape for Proprietary Estoppel Post-Guest v Guest

The Rise of Proprietary Estoppel in Family Farm Disputes

Proprietary estoppel, once considered a claim of last resort, has more recently made headlines as the “golden ticket” for “cowshed Cinderellas”. In this week’s edition of Field Notes, Raiff Andrews considers whether there is any greater consistency in the types of remedy the court can award in a successful proprietary estoppel claim, particularly in a farming context.

A claim in proprietary estoppel may arise, in essence, where Party A makes a promise to Party B (such as a promise of land) and Party B acts in reliance on that promise to their detriment. Over the last 20 years claims in proprietary estoppel, particularly those involving family farms, have become increasingly common. Driven in part by the rise in value of agricultural land and assets, as well as a growing awareness of proprietary estoppel as a potential avenue for a claim by a disappointed promisee, we have also seen a growing number of claims brought during the landowners’ lifetime.  Notable proprietary estoppel cases involving farms include Thorner v Major [2009], Gillet v Holt [2001], Davies v Davies [2016] and Habberfield v Habberfield [2019], with Gillet, Davies and Habberfield all brought within the lifetime of the landowner (or one of two joint owners in Habberfield). The line of authorities consistently shown that the court’s purpose in a proprietary estoppel claim was to remedy the unconscionability of the promisor’s decision to renege on their promise. But where the authorities have been less clear has been in relation to the form and extent of the remedy the claimant should be awarded. Specifically, should the remedy satisfy the claimant’s expectation (with adjustments if necessary), or should it aim only to compensate him for the detriment he has suffered in reliance on the promise.

It was this precise issue the Supreme Court was required to determine in the recent case of Guest v Guest [2023], concerning yet another family farm dispute.

In Guest, the claimant lived in a cottage on his parents’ farm and worked for low wages in the expectation that he would inherit an unspecified part of the farm after his parents’ death, sufficient to permit him to continue a viable farming business. The claimant brought his claim after falling out with his parents and being made aware his expectations would no longer be met.

The majority judgment in Guest (given by Lord Briggs with Lady Arden and Lady Rose in agreement) confirmed that the essential aim of a claim in proprietary estoppel was to rectify the unconscionability that results from A repudiating their promise to B and that the starting assumption (but not presumption) is to enforce B’s expectations. As stated by Lord Briggs in Guest, ‘it is the repudiation of the promised expectation’ that constitutes the unconscionable conduct. This contrasted with the dissenting judgments of Lord Leggatt and Lord Stephens, who argued that the essential aim was to remedy the detriment suffered by B as a consequence of A’s assurances.

This Field Note considers the findings in Guest, in the light of two of the most recent judgments to follow it, which have concerned family farming businesses, Winter v Winter [2024] and Armstrong v Armstrong [2025].

What are the elements of a successful proprietary estoppel claim?

Guest (re)confirmed that the essential tenets of a claim in proprietary estoppel are: 

• Clear assurances from A made to B
• Reliance by B on A’s assurances
• A detriment suffered by B as a result of relying on the assurances of A and
• That it would be unconscionable in the circumstances for A to resile from the assurances/promises made. 

When all these criteria are met, the appropriate remedy may arise in different forms. For example, it may be a personal right (such as a licence) or a proprietary right (such as the freehold title). Proportionality is also important.

In what circumstances can a successful Claimant expect to be awarded what they have been promised?

In a continuation of the trend over the last 20 years, Armstrong (decided earlier this year) involved a dispute over a family farm. In this case, claimant B’s deceased father, A, had made assurances over a number of years that B would inherit the family farm. B relied on these assurances from A to his detriment.  Amongst other examples, in reliance on the promises made, B chose not to attend university to study engineering but rather going to agricultural college specifically with a view to working on the farm. Shortly before his death, A executed a will that disinherited B and repudiated B’s reasonable expectation of inheritance. The court held that A’s conduct in making this new will was unconscionable in the circumstances and the claim in proprietary estoppel succeeded. The purpose of the remedy awarded by the court was to fulfil B’s expectation of inheriting the farm.

The judgment in Armstrong followed the majority decision in Guest, with the judge in Armstrong stating that: ‘I have determined that the repudiation of A's promise was unconscionable. I therefore start with the assumption, but not presumption, that the simplest way to remedy the unconscionability is to hold A's estate to the promise’.

Will the remedy be commensurate to the detriment suffered?

The assumption that A will be held to his promise does not mean that, where there is a successful proprietary estoppel claim, B’s expectations will necessarily be enforced. Lord Briggs in Guest held that, whilst proportionality was not the basis of a claim, it was an important factor to take into account in any remedy the court awarded, as summarised in Crabb v Arun District Council [1976]. In Crabb, Scarman LJ held that it was an essential requirement that the expectation must not be out of all proportion to the detriment suffered.

In Armstrong, it was argued by the defendants that there could not have been a reasonable expectation that the farm was to be inherited free from any debt. This argument succeeded and it was determined that B receiving the farm free of the debt was not required to prevent an unconscionable result. Rather, it was determined that the assurances from A were clear, but that the farm businesses were burdened by debt when B agreed to run them. In his judgment, Mr Andrew Sutcliffe KC reiterated the words of Lord Briggs in Guest that ‘it will be a very rare case where the detriment is equivalent in value to the expectation’.

How is detriment assessed?

The Court of Appeal in Winter paid particular attention to the nature of the detriment required for a successful claim. The High Court in Winter concluded that B had relied on assurances from A in devoting their working lives to the farm business for relatively low pay. As such, that it would be unconscionable for A's estate to renege on those assurances.

On appeal, it was argued by A, that B had not suffered a determinant. Appearing for the Appellant, Mr Alex Troup KC argued that the trial Judge had failed to explain why it was detrimental and, in any event, failed to weigh any such detriment against the financial benefits.

In contrast, Mr Hugh Sims KC appearing for the Claimant Respondents, argued that the trial Judge was correct and was entitled to find that the lifelong commitment to the family business was sufficient to satisfy the test of detrimental reliance. The Court of Appeal in Winter found in favour of this argument. The Court of Appeal recognised that the trial Judge was correct to identify that the lifetime commitment by B to working on the farm was “not capable of being quantified”. The essential exercise for the Court, when considering detrimental reliance, is to “weigh any non-financial disadvantage against any financial benefit even where the disadvantage is not susceptible to quantification”. In this case, the lifetime commitment of B to the farm business was ruled to have outweighed any financial benefits. In dismissing the appeal, the Court of Appeal’s decision in Winter is consistent with recent case law concerning how detrimental reliance is assessed.

For example, Lewison LJ in the Court of Appeal decision in Habberfield upheld the decision at first instance of Birss J, who had awarded a monetary sum as a proxy for the promised inheritance of part of the contested farmland. Lewison LJ agreed that decades of B’s life in contributing to the farm were not ‘susceptible of quantification’. Similarly in Guest, Lord Briggs highlighted that ‘…however precisely it might be described, its lifetime consequences were extremely difficult to value’.

What remedies can be awarded in proprietary estoppel claims during the landowner’s lifetime?

The majority decision in Guest concluded that the promise (and the claimant’s expectation) should be specifically enforced, but that there should be some adjustment for the fact that he was receiving fulfilment of the promise while his parents were still alive rather than on death, which had been the promise made. The majority gave the parents the choice between either: a non-financial remedy comprising a share in the farm and business held on trust for Andrew until his parents’ death and in which his parents were to have a lifetime interest; or a financial remedy following a sale of the farm now, with a discount for early receipt.

What are the Main Takeaways from Winter and Armstrong?

Winter and Armstrong show that remedying the unconscionability to satisfy the equity remains at the heart of the doctrine of proprietary estoppel. The starting assumption in both Winter and Armstrong, consistent with Guest, was to seek to fulfil the expectations of B. In this regard, there is a greater degree of certainty for individuals either pursuing or confronting a claim in proprietary estoppel. However, the application of proportionality between the expectation and the detriment remains complex and highly fact specific, where each case requires careful scrutiny to ensure equity is restored.

If you’re keen to make succession plans to avoid the risk of future contention, want to understand how your property is held or are concerned about a future or current proprietary estoppel claim the team here at Charles Russell Speechlys, including contentious and non-contentious specialists, would be happy to help. We invite you to contact Raiff Andrews, Maddie Dunn, Tristram van Lawick or your usual contact at Charles Russell Speechlys.

Field Notes is Charles Russell Speechlys’ weekly agricultural law blog, sharing plain-English insight into the legal and policy issues affecting agriculture, agricultural land and rural business life. From hints and tips on avoiding agricultural disputes, pitfalls to keep an eye out when planning for tenancy or family agri-business succession, to the latest agricultural legislative or policy changes and the most interesting farm-related court decisions, Field Notes makes the complex more understandable, always grounded in the realities of life on (and off) the land.

Field Notes comes out every Wednesday. Previous editions of Field Notes include:

• One Year On: Agricultural Holdings Act 1986 succession after the Agriculture Act 2020 reforms
• Cheltenham: Where Clarkson Meets Covenants
• Arbitration Act 2025: what it means for farmers, landowners and rural disputes
• Renters’ Rights Bill: what rural landowners need to know
• Nature-friendly practice or unnatural risk: beavers, natural nuisance and measured duty, the rule in Rylands v Fletcher