Contract variation in the common law

This note analyses the UK Supreme Court’s decision in Rock Advertising Ltd v MWB Business Exchange Centres Ltd, a case that confirms the long uncertain ability of ‘No Oral Modification’ clauses to exclude informal variations in English law. This note argues that, while the Court was correct to reject the putative oral variation in question, the majority’s description of the law is unsatisfactory because of its detachment from wider contract law principle, and compares unfavourably with the alternative ratio by which Lord Briggs reached a concurring outcome. This note also comments on the Supreme Court’s (cursory) treatment of the portentous Court of Appeal decision in Williams v Roffey Bros, which has reformulated the law on contract variation across common law jurisdictions. The Court acknowledged, but declined to resolve, the tensions Roffey introduced in to the law on part payment of debts. While it is unfortunate that the opportunity to resolve these tensions was missed, this note endorses the Court’s (obiter) rejection of the analysis by which the Court of Appeal below sought to extend Roffey to the part payment of debts.