Restitution has emerged over the last 50 years as an essential component in the modern law of obligations. Its central concerns are the reversal of unjust enrichment and the unscrambling of defective transactions. A major difficulty with studying restitution is terminological. Whereas the older cases utilize techniques such as ""actions for money had and received"" and ""constructive trusts"", modern cases and juristic writings speak of ""unjust factors"" and ""incontrovertible benefit"". This volume guides the reader through the often impenetrable language to an appreciation of the leading cases, and a clearer understanding of the practical difficulties of restitution claims. Cases cover issues ranging from the deceptively simple example of mistaken payments to the complicated fall-out of corporate collapse, as in the ""Barlow Clowes"", ""Polly Peck"" and ""Maxwell"" cases.