This book is the spiritual successor to Stevens’ ground-breaking article: “The unjust enrichment disaster” (2018) 134 LQR 574. That article had a profound impact on unjust enrichment scholarship and practice around the common law world and compelled unjust enrichment loyalists to defend the unity of their subject. Indeed, it led Professor Andrew Burrows, prior to his appointment to the Supreme Court, to publish “In defence of unjust enrichment” [2019] CLJ 521, in which he attempted to defend the orthodox approach in the face of “significant scepticism about the utility of recognising a law of unjust enrichment” (p.522). The Laws of Restitution represents the culmination of Stevens’ long reflection and thinking about the subject(s).

The primary claim Stevens advances is not entirely new. Others have argued before that the “unjust enrichment” project is misguided: see eg S Hedley, “Unjust enrichment as the basis of restitution—an overworked concept” (1985) 5 LS 56; P Jaffey, The Nature and Scope of Restitution (Oxford, 2000), 15–21; P Watts, “‘Unjust enrichment’—the potion that induces well-meaning sloppiness of thought” (2016) 69 CLP 289; cf R Stevens, “Faute de mieux”, in S Peari and W Swain (eds), Rethinking Unjust Enrichment (Oxford, 2023). But, as Professor Charlie Webb notes in his contribution to this review, one of the important aspects of Stevens’ contribution is the identity of the messenger. Stevens is the Herbert Smith Freehills Professor of Private Law at the University of Oxford; he has taught unjust enrichment for 30 years, 10 of which were alongside Professor Peter Birks. At one point, Stevens was an acolyte of the unified approach to unjust enrichment. Stevens’ crisis of faith is therefore significant. That such a prominent (former) supporter of the orthodoxy has reason to think something has gone wrong gives everyone interested in the subject pause for thought.