The doctrine of undue influence has undergone reconsideration by the House of Lords in Royal Bank of Scotland v Etridge (No 2) [2004] 4 All ER 449. The case was an attempt by the House of Lords to clarify the law and dispel some of the misconceptions that have developed in the law over the last 200 years. This thesis will examine the law of undue influence. It will examine the theoretical basis of undue influence, the general misconceptions in the law, the impact of the Etridge case, and related doctrines of duress and unconscionability. Given the developments in the law due to Etridge, issues regarding simplification of the law will be examined. The three doctrines share much in common, and issues of fusion of one or all of the existing doctrines will be considered, and whether this would lead to a better understanding of the law in this area.