The law of unjust enrichment admits a novel policy motivated unjust factor called the policy against accumulation. This applies where a claimant (R) receives a benefit, or has the right to recover a debt or damages from another party (X), and receives or has the right to receive value in respect of the same debt or damage from a third party (Y). The claimant is rarely permitted to retain both the transfers made by X and Y. In other words, R (...) may not accumulate and one transfer must be reversed. This article contends that the right of a third party to participate in damages recovered by the claimant is best explained by the policy against accumulation. The focus of this inquiry is to illustrate the operation of this novel unjust factor by placing in parallel three House of Lords decisions: Hunt v Severs [1994] 2 AC 350, Dimond v Lovell [2000] 2 WLR 1121, and Lord Napier and Ettrick v Hunter [1993] AC 713. (shrink)