64. Recovery of money paid under a mistake at common law.

The law relating to recovery of mistaken payments has a long history, going back to the so-called 'common counts' for money had and received to the use of the plaintiff1, and before that to the old law of account2. Along with quantum meruit, quantum valebat, and other counts, it became a part of the law known as quasi-contract3, which has now developed into the law of restitution4, the central principle of which is the reversal of unjust enrichment5. Under the umbrella of this principle, other areas of both common law and equity have been united with that relating to