## Facts

- The dispute arose from an informal arrangement between a father, Lewis Llewellyn, and his son, Thomas Llewellyn.
- The father verbally promised his son a portion of his Welsh estate known as the “Penllwyn Estate.”
- In reliance on this promise, the son took possession of the land and made significant improvements, including constructing a house and other buildings.
- Upon the father’s death, his will did not formally transfer the Penllwyn Estate to the son; rather, the estate passed to the widow and other heirs, who sought to reclaim the land.
- The son brought a claim in the Chancery Court, asserting entitlement due to his reliance and improvements based on the father’s promise.

## Issues

1. Whether the informal promise by the father, in the absence of a written agreement, could create an enforceable interest in land for the son.
2. Whether the son's reliance and improvements on the land, based on the promise, gave rise to an equitable interest enforceable against the father's estate.
3. Whether it would be unconscionable to allow the father's estate to reclaim the land after the son's detrimental reliance.

## Decision

- The Chancery Court held that equity would intervene where there was a clear and unequivocal promise, reliance on that promise, and detriment suffered by the promisee.
- The court found the father’s verbal promise to be sufficiently clear and that the son had relied on it by making substantial improvements to the land.
- It was determined that it would be unconscionable for the estate to reclaim the land after the son's detrimental reliance.
- The court granted the son an equitable interest in the property, enforcing the informal promise despite the absence of a formal written agreement.

## Legal Principles

- For proprietary estoppel to arise, there must be (1) a clear promise or assurance, (2) reliance by the promisee, and (3) detriment suffered as a result of that reliance.
- Equity will enforce informal promises relating to land when strict adherence to legal formalities would result in an unjust outcome.
- The doctrine of proprietary estoppel mitigates the rigidity of the common law in the context of land and property disputes.

## Conclusion

Dillwyn v Llewellyn (1862) 4 De GF & J 517 established the essential elements of proprietary estoppel, allowing equitable enforcement of informal promises where reliance and detriment would make it unconscionable to deny the claimant relief, and remains a foundational authority in English property law.

Dillwyn v Llewellyn (1862) 4 De GF & J 517 (Ch)