Refinancing transactions are one of the most common incidents of commercial life. The degree of uncertainty which surrounds the legal consequences of such transactions constitutes a weakness in our commercial law. At the heart of this uncertainty lies the doctrine of subrogation. The “tangled web”1 of case law on subrogation has been described as formidably confusing.2 For many years, subrogation has lurked somewhat uncertainly at the periphery of the law of restitution. Dr Charles Mitchell’s book on the subject3 did much to bring it into focus and position it in its rightful place as an important part of the law of unjust enrichment.4 The House of Lords recently had occasion to look afresh at subrogation in Banque Financière de la Cité v. Parc (Battersea) Ltd 5 (henceforth “BFC v. Parc”). This case provides important clarification on a number of fundamental points. This paper seeks to analyse the important issues raised by the case as well as to look at some of the related problems which have troubled the law of subrogation for so many years. The focus of the paper concerns one particular instance of subrogation, namely, where one party, S, loans another party, PL, the money to discharge a secured debt owed to a third party, RH.6 This is an example of what has become known as reviving subrogation,7 so called because the effect of the doctrine is to revive some or all of RH’s extinguished rights and vest them in S, giving him enforceable rights against PL and/or