Proprietary vs Promissory Estoppel Explained
Promissory estoppel and proprietary estoppel are two important legal principles in English law that prevent unfair outcomes when promises are broken.
While the names are often confused, they apply in very different circumstances.
- Promissory estoppel stops someone from going back on a promise when it would be unjust, even if there is no formal contract.
- Proprietary estoppel applies more specifically to promises relating to land or property, where a person has relied on an assurance and suffered detriment as a result.
Both doctrines are part of equity, the branch of law that seeks to achieve fairness. In this article, we explain what each means, trace their origins, highlight the differences, and explore the remedies available.
The Origins of Estoppel in English Law
The word “estoppel” comes from the Norman French “estoupail”, meaning “stopper”.
The doctrine developed in English law to stop one party from contradicting their earlier words or conduct if it would be unjust to do so.
Traditionally, estoppel was used as a defence, often described as a “shield” rather than a “sword”. Over time, however, courts recognised that in certain circumstances, estoppel could also be the basis of a claim. Proprietary estoppel is the clearest example of this.
What Is Promissory Estoppel?
Promissory estoppel prevents a person from going back on a promise, even without a contract, if the following conditions are met:
- A clear and unambiguous promise or assurance was made
- The other party relied on it
- That reliance caused detriment or unfairness
It often arises in contract law, where one party promises not to enforce their strict legal rights. For example, if a landlord tells a tenant they will not increase rent, the landlord may later be prevented from demanding backdated increases if the tenant relied on that assurance.
Promissory estoppel is generally used defensively. It prevents unfair enforcement of rights but does not usually allow a person to bring a claim in its own right.
What Is Proprietary Estoppel?
Proprietary estoppel is different. It applies where someone has been promised rights over land or property, relied on that promise, and would be unfairly disadvantaged if the promise were broken.
The courts generally require three elements:
- A representation, assurance, or promise was made
- The person relied upon it
- They suffered detriment as a result of that reliance
Unlike promissory estoppel, proprietary estoppel can be the basis of a claim. It frequently occurs in inheritance and farming disputes, where one family member has worked for years on the understanding that they will inherit land or property.
Proprietary Estoppel vs Promissory Estoppel: The Key Differences
Because the names are so similar, many people confuse the two. Here is how they differ:
| Focus | General promises (often contractual) | Rights over land or property |
| Legal Relationship | Usually requires an existing one | No prior legal relationship needed |
| Typical Role | Used as a defence (“shield”) | Can form a claim (“sword”) |
| Remedies | Stops enforcement of rights | Can grant property rights or compensation |
| Example | A landlord promising not to enforce rent | A parent promising land to a child who builds a house on it |
The most important distinction is this: promissory estoppel is usually defensive, while proprietary estoppel can be used to bring a claim.
How Clear Must the Assurance Be?
In Thorner v Major [2009 UKHL 18], the House of Lords confirmed that an assurance must be “clear enough” rather than unequivocal. The courts look at promises in their proper context.
For example, a casual comment may not be enough, but repeated assurances over the course of a few years could be enough to found an estoppel claim.
Examples of Detrimental Reliance
Courts carefully examine whether a person has suffered detriment by relying on a promise.
- No estoppel found: In Dobson v Griffey [2018 EWHC 1117], the claimant gave up a full-time job to work on a farm, expecting lifelong rights to live there. The court held that the expectation was not based on the defendant’s conduct, so no estoppel arose.
- Estoppel applied: In Inwards v Baker [1965 2 QB 29], a father told his son he would leave him land in his will. The son built a home on the land and lived there for 30 years. When the father left the land to someone else, the court ruled the son could not be evicted.
- Recent example: In Habberfield v Habberfield [2019 EWCA Civ 890], a daughter worked on her parents’ farm for years, relying on assurances she would inherit. The court upheld her claim for proprietary estoppel and awarded her £1.17 million.
These cases show how fact-sensitive estoppel claims can be.
Remedies Available
One of the most important features of proprietary estoppel is the court’s flexibility in deciding remedies. Judges balance the expectation created by the promise against the detriment suffered.
Typical remedies include:
- Granting ownership of property
- Awarding a life interest (the right to live in a property for life)
- Providing financial compensation
- Adjusting the award to be proportionate rather than always giving the full promised inheritance
A key case on proportionality is Jennings v Rice [2002 EWCA Civ 159], where the claimant had cared for an elderly woman for years after being promised “he would be alright”. Instead of awarding him the whole estate, the court granted £200,000, reflecting both the detriment and the fairness of the situation.
FAQs About Estoppel
What is promissory estoppel in simple terms?
It prevents someone from going back on a promise if another person has relied on it and would be treated unfairly otherwise.
What is proprietary estoppel in simple terms?
It applies when a person is promised rights over land or property, relies on that promise, and suffers detriment if it is not kept.
What is the main difference between proprietary and promissory estoppel?
Promissory estoppel usually applies in contractual contexts and is used as a defence. Proprietary estoppel relates to property rights and can be used as the basis of a claim.
Can promissory estoppel create a contract?
No. Promissory estoppel does not create new legal rights. It prevents the enforcement of existing ones where it would be unfair.
Is proprietary estoppel common in inheritance disputes?
Yes. It commonly happens where children or relatives work on family property or farms for years, relying on assurances they will inherit, only to find themselves excluded by a will.
What counts as detriment in estoppel cases?
Detriment can include financial loss, giving up career opportunities, unpaid labour, or making life decisions such as building a home based on a promise.
When to Seek Legal Advice
If you have relied on a promise or assurance, particularly one involving property, and suffered detriment as a result, you may have grounds for an estoppel claim.
These cases are highly fact-specific, and early legal advice can save time, money, and stress.
At Bennett Griffin, our Wills, Trusts & Estate Disputes in Worthing and Chichester have extensive experience with both proprietary and promissory estoppel. We provide clear, supportive guidance to help you understand your options and protect your interests.
Call us on 01903 229999 or 01243 256370.
Alternatively, you can email info@bennett-griffin.co.uk and one of our team will get back to you shortly.