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[1874] LR 18 Eq 315. The principle espoused by this case is highly technical, roundly criticised, and rarely exercised in practice. Howerver, it has been relied on in a number of later cases, so it remains important.

The principle of Strong v Bird is that, in certain circumstances, equitable discretion will be refused when it would normally be granted, allowing an earlier common-law rule to prevail. The common-law rule is that if a testator appoints to be his executor someone that owes him money, the debt is cancelled when the testator dies. Why? Well, since the executor is responsible for calling in debts to the testator's estate, he will be put in the invidious position of having to sue himself for the debt. Common-law rulings cancelled the debt to avoid this anomaly. Later equitable decisions made the executor responsible for his debts to the estate, despite the oddity of having to sue himself. In this case, because the testator had manifested an intention to remit the dead in his lifetime, and had maintained that intention up until his death, then the common law rule was allowed to stand, and the debt cancelled.

See Imperfect Gift and Constitution of Trusts for further discussion.