Jennifer Meech considers the Supreme Court decision in Guest v Guest [2022] UKSC 107 and the proper remedy for a claim in proprietary estoppel


For a claim in proprietary estoppel to succeed, the claimant must establish that the defendant promised them an interest in property; that they reasonably relied on that promise to their detriment; and that it would be unjust for the defendant to resile from their promise.

Once they have established those elements the court has a discretion as to the proper remedy. What is the starting point for that remedy? Is it the value of the promised interest or the value? Or is it the value of the claimant’s detrimental reliance? For two decades this question has been a mainstay of debates between property law academics. In Guest, the Supreme Court provides their answer. 

The case

Like many proprietary estoppel cases, Guest involved a dispute about a family farm. The claimant was the eldest son of the defendants. At trial the claimant established that he had a valid claim in proprietary estoppel:

  • he had been consistently led to believe by his father (with the tacit support of his mother) that he would succeed to the farming business and would inherit a substantial share of the farm; and
  • he had reasonably relied on those assurances and worked on the farm for many years for little financial reward.

First instance

At first instance Judge Russen QC, sitting as a judge of the Chancery Division, ordered that the defendants make a lump sum payment to the claimant comprised of 50% after tax of the market value of the farming business and 40% after tax of the value of the farm itself. This remedy was intended to give the parties a ‘clean break’: the parents were still living and the judge felt that it would be inappropriate to order them to leave the farm in the short term.

The defendants did not seek to appeal the finding that the claimant had made out a claim in proprietary estoppel but sought to overturn the court’s decision on remedy.

The Court of Appeal refused the parents’ appeal.

Supreme court

The question for the Supreme Court was: What is the correct remedy for proprietary estoppel? Was it the promised property interest? Or was it compensation for the losses suffered by the claimant when relying on the promise (the detriment)?

The Supreme Court was split. The majority (Lord Briggs JSC with whom Lady Rose JJSC and Lady Arden agreed) held that proper remedy was based (usually) on the promise. The minority (Lord Leggatt JSC (with whom Lord Stephens JSC agreed) preferred the detriment-based analysis.

The majority and the minority both considered the purpose of the doctrine and its remedy. Lord Briggs stated that it was intended to deal with “the unconscionability constituted by the promisor repudiating his promise” (at [13]) whereas Lord Leggatt considered that the purpose was “to avoid the detriment to [the promisee] which will result from [their] reasonable reliance on the promise if [they are] not given this right” (at [189]).

Lord Briggs’ identification of the purpose as set out above led to the conclusion that the remedy should be (in most cases) to prevent the defendant from resiling from their promise. The remedy analysis should “normally start with the assumption (not presumption) that the simplest way to remedy the unconscionability constituted by the repudiation is to hold the promisor to his promise” (at [75]).

However, enforcing the promise is not always the correct remedy. Lord Briggs added (at [76]) the caveat that if the defendant asserts and proves (the burden being upon them) that enforcing the promise “would be out of all proportion to the cost of the detriment to the promise, then the court may be constrained to limit the extent of the remedy”. Although he emphasised that comparing the promise and the detriment was not a purely financial comparison (at [73]): “[m]odern capital values of farmland are typically so high that the farm would always be worth much more than any valuation of the detriment. 

If a promise-based remedy is ‘out of all proportion’, the next step is not necessarily to identify and award compensation for detriment. Lord Briggs accepted (at [79]) that this meant that there was a “wide range of options with little in the way of rules as a guide” but “the court will just have to do the best that it can”. He concluded (at [80]):

“In the end the court will have to consider its provisional remedy in the round, against all the relevant circumstances, and ask itself whether it would do justice between the parties, and whether it would cause injustice to third parties. The yardstick for that justice assessment will always be whether, if the promisor was to confer that proposed remedy upon the promise, he would be acting unconscionably. ’Minimum equity to do justice’ means, in that context, a remedy which will be sufficient to enable that unconscionability question to be answered in the negative”

The majority held that the correct remedy in the instant case was for the parents to have a choice between (a) the payment of a limited sum and a structure that allowed them to stay on the farm whilst they lived, or (b) an immediate payment of a larger sum. The larger sum would be based on the value of what the claimant had been promised but discounted to account for the fact that he was receiving it earlier than expected. Lord Briggs did not feel able to determine either the structure or the discount and so those issues were remitted to the High Court.

The minority were very critical of the majority’s view. At [164] Lord Leggatt stated that “[t]o give judges no clearer mandate than to do what that think just or necessary to avoid unconscionability is a recipe for inconsistent and arbitrary decision making. This is itself a source of injustice”. At [181] he continued “Legal principle has been replaced by the portable palm tree”. He would prefer that judges consider the promise and the detriment and (at [256]) “if on the facts both are practicable the court should adopt whichever method results in the minimum award necessary to achieve that aim”.


This case is useful in that it lays to bed a significant academic debate but it is not a complete crib for lawyers advising on proprietary estoppel claims.

In order to advise on the likely remedy the following questions will need to be addressed:

  1. What was promised (this will not always be clear, particularly in a familial context)?
  2. If the promise was of a future interest, when was the promisor to obtain that interest?
  3. What is the value of the promised interest?
  4. What discount should be applied for accelerated receipt (the Supreme Court decision does not answer this question)?
  5. What was the value of the detriment?
  6. Can it be said that the value of the interest promised is out of all proportion to the cost of the detriment?
  7. If it was, what will the court order?

Lord Briggs made clear that the answer to question 6 is not merely a monetary assessment. The cost of land compared to wages, particularly in farming or in caring professions, means that the value of what was promised is often going to be significantly more than what was given up but that will not necessarily make it ‘out of all proportion’. However, perhaps if someone was promised an inheritance in exchange for care and the death occurred very shortly after the promise the disparity would be made out. Or perhaps if the claimant had no other prospects such that the detriment was of no value.

If the disparity is present, or might be, the breadth of possible remedies is likely to be very wide. In such cases the risks of litigation for both sides are very significant and settlement should be sought early. It may be useful in such claims for the parties to consider Early Neutral Evaluation, alongside other ADR options, to settle the dispute.