Proprietary estoppel following Guest v Guest [2022] UKSC 27

October 28, 2022

By Hateema Zia and Bill Hanbury

“One day my son, all this will be yours”: a promise made by a father to his son, and then broken after their relationship deteriorated. The son left, and the Parents changed their will excluding him, leading the son to issue proceedings on the basis of proprietary estoppel.

In simple terms, proprietary estoppel stops a person from going back on their promise. It relates to the ownership of property, including land, objects and chattels but in most cases it relates to land-hence “proprietary estoppel”. Although the proprietary nature of the remedy can cause confusion – whereas a constructive trust is one of immediate interest in land proprietary estoppel merely provides an opportunity to satisfy the court has an equity capable of affording one that interest. It does not necessarily follow that the court will accede to that request even if it finds the other party estopped from denying the promise in question.

Proprietary estoppel allows B (the Promisee) to enforce a promise made by A (the Promisor) in relation to the ownership of lands where B has reasonably relied on that promise and would suffer detriment if the promise was not fulfilled even though the promise is not supported by consideration as would be recognised in the law of contract.

In the 108 pages, 282 paragraphs, the Supreme Court’s judgment in Guest v Guest, handed down on 19 October 2022, the justices suggest the proper basis for awarding a remedy in proprietary estoppel cases.  The reader might expect the author at this point to say this is a rare opportunity for the Supreme Court to consider the law but in fact there have been numerous cases going to the highest court in recent years – most of them in the matrimonial context and most concerned with the substantive requirements rather than the relief which flows from establishing proprietary estoppel.

Background facts

The dispute was between parents (David and Josephine) and their eldest child (Andrew). They were a farming family. Andrew lived and worked on the farm for the most part of his working life with the ‘expectation’ that one day he would inherit the farm and continue to farm there until he passed it on to his own children.

In around 2008 the relationship between Andrew and his parents deteriorated. In 2015, the parents made new wills removing Andrew’s inheritance. Andrew issued proceedings, on the basis of proprietary estoppel, a share in the family farm or its monetary equivalent.

The trial judge’s findings

The judge found that although there was never an ‘express’ promise made to Andrew by his parents, words such as “one day my son, all this will be yours”, said over many years encouraged an ‘expectation’ which was equivalent to a promise.

The parents were ordered to make an immediate payment of £1.3m to satisfy Andrew’s expectation as to his future inheritance (subject to certain adjustments). This was calculated as 50 percent of the value of the dairy farming business plus 40 percent of the value of the freehold land and buildings at the farm.

Given the family breakdown the judge decided that a ‘clean break’ was necessary. The effect of the award was that the farm would have to be sold and Andrew would receive his share during his parents’ lifetimes and not as an inheritance. In other words, the clean break solution accelerated Andrew’s inheritance.  His expectation was that he would only inherit on his parents’ death, but now he was getting everything early.

The Court of Appeal’s decision

The parents argued that the trial judge was wrong to give Andrew a remedy which was based on his expectations. Instead, his parent’s argued that the judge should have awarded a remedy based on Andrew’s contribution to the value of the farm or the detriment that he had suffered (his loss of opportunity to work elsewhere).

They also argued that the remedy wrongly accelerated Andrew’s expectation, as he had not expected to receive an interest in the farm until his parents died.

The Court of Appeal dismissed the appeal, holding that it was appropriate to order a remedy by reference to Andrew’s expectation and that the trial judge was entitled to make the order he did. The parents appealed to the Supreme Court.

The Supreme Court’s decision

The Supreme Court was asked to decide:

  1. Whether a successful claimant’s expectation was an appropriate starting point when considering remedy; and
  2. Whether the remedy granted went beyond what was necessary in the circumstances.

The court was divided (by a 3-2 majority), and the appeal was allowed in part. The basic division was between the majority holding that the claimant’s expectation must be satisfied and the minority holding that the court’s function was largely to compensate him for his reliance (detriment) on the promise which would not be fulfilled.

Lord Briggs (who gave the leading judgment) with whom Lady Arden and Lady Rose agreed, allowed the appeal, substituting alternative remedies of either:

  • Putting farm into trust for the children with a life interest to the parents; or
  • Paying equitable compensation now but with a deduction for accelerated receipt.

The choice of remedy was for the parents, but in default it is to be remitted to the Chancery Division for determination.

Lord Briggs rejected the idea that the aim of a remedy for proprietary estoppel is (or has been) to compensate for the detriment suffered by the promisee as its purpose was to remedy unconscionability mainly by satisfying expectation. Accordingly, the parents’ argument was rejected. However, the remedy should not be, without ‘some good reason’, out of all proportion to the detriment, if that can readily be identified. Lord Briggs discussed whether there should be a spectrum between expectation and detriment as the basis for relief based upon the length of the period of reliance on the promise before it is repudiated. However, in Guest the claim lay at the expectation end of the spectrum in any event given the length of time he had relied on the promise.

Lord Leggatt, with whom Lord Stephens agreed, would have also allowed the appeal, but for different reasons. Lord Leggatt considered that the core principle underpinning relief for proprietary estoppel is to prevent a party going back on a promise while ensuring that the party who relied on the promise will not suffer a detriment as a result of that reliance. On this basis he would have substituted the remedy, by way of quantification of Andrew’s reliance loss, as a payment of £610,000.

Test for appropriate relief in proprietary estoppel

In simple terms therefore, at least in promise based estoppel one should start by asking: Would going back on the promise be unconscionable in all the circumstances?

If “yes” should the court:

  1. Enforce transfer of property in question; or
  2. Provide monetary equivalent

Option 1 may not be available in the following situations:

  1. The promisor had sold the promised property,
  2. The property is required for the promisor’s own occupation,
  3. Enforcement of the promise would cause injustice to a third party (because they have an interest in it or have a dependency upon its continued use).


  1. The court does not have the power to award a claimant any more than he has been promised.
  2. If the remedy chosen would be out of all proportion to the detriment to the promisee, then the court ‘may’ need to limit the remedy.
  3. If the remedy involves the acceleration of a future promised benefit, it will generally require a discount for accelerated receipt.
  4. The court should consider in the round whether a particular remedy would do justice in the circumstances, by considering whether the promisor would be acting unconscionably if they were to confer the proposed benefit on the promisee rather than the court.

Application of Guest in practice

Lord Briggs took a creative approach and created remedies to suit the circumstances of the case. For example, a ‘clean break’ was ordered because the son had left the farm. But what happens in a situation where the parties have not left the property and do not want to sell?

The case demonstrates how difficult it is to put a value to the detriment suffered, and further clarity on the matter is required, or perhaps the purpose of the judgment is to provide flexibility in applying the principles of equitable relief?

Ultimately the power is given to the promisor to decide how they can make good their promise. This means the remedy will be different depending on both the circumstances, and what is chosen.

To the authors, it appears that there is a great deal to commend Lord Leggatt’s approach. The core of estoppel is after all the removal of injustice. Arguably the outcome in Guest disproportionality  compensates one beneficiary of an estate at the expense of others.

Bill Hanbury specialises in property litigation and local government law including local government finance and is currently writing a new edition of his book on Boundary Disputes for the Law Society and Hateema Zia is a pupil barrister in the Business and Property Department.