## Facts

- The plaintiff and defendant were in a long-term relationship and had two children together.
- The plaintiff purchased a house for the defendant and their children, intending it to be their family home.
- Following the end of the relationship, the plaintiff sought possession of the property.
- The plaintiff argued that no formal agreement conferred a legal interest in the property to the defendant.
- The defendant claimed that the plaintiff’s promise to provide housing created a binding obligation, relying on the promise by moving into the property and caring for the children.

## Issues

1. Whether a promise to provide accommodation for a cohabiting partner and children, in the absence of a formal written agreement, creates a legally binding obligation.
2. Whether the parties’ conduct and intentions could give rise to an enforceable agreement through implied contract or constructive trust.
3. Whether equity should intervene to prevent unjust enrichment and ensure fairness in informal family arrangements concerning property.

## Decision

- The court found that the informal family arrangement could give rise to a legally binding obligation.
- The plaintiff’s promise to provide housing and the parties’ conduct demonstrated sufficient intention to create an implied contract.
- The court held that a constructive trust arose in favour of the defendant and their children, granting the defendant a beneficial interest in the property.
- The plaintiff was prevented from unjustly reclaiming the property, given the defendant’s reliance and detriment.

## Legal Principles

- Family arrangements, even if informal, can result in legally binding obligations if there is clear evidence of an agreement and reliance.
- An implied contract may arise based on the conduct and intentions of the parties, not requiring a formal written agreement.
- Constructive trusts are used by courts as equitable remedies to prevent unjust enrichment in cases of reliance on promises relating to property.
- The doctrine of proprietary estoppel supports the prevention of a party reneging on a promise if the other party has relied to their detriment.
- Reliance and detriment are important in establishing enforceable obligations in familial and cohabitation contexts.

## Conclusion

The Court of Appeal in Tanner v Tanner confirmed that informal family arrangements regarding property can give rise to enforceable obligations, relying on implied contract principles and constructive trusts to ensure equitable outcomes when one party relies on a family promise to their detriment.

Tanner v Tanner [1975] 1 WLR 1346