Illegality after Patel v Mirza

English law on illegality in private law (eg illegal contracts) has long been regarded as both difficult and unsatisfactory. In 2016, the Supreme Court, sitting as a panel of nine, looked at the area again in Patel v Mirza. Here £620,000 had been paid for the defendant to bet on share prices using inside information (which, if carried out, would constitute the crime of insider dealing). The agreement was not carried out because the information was not forthcoming. Was the claimant entitled to repayment of that money? In answering that question, a majority of the Supreme Court set out a controversial new approach to this area of the law, which was vigorously rejected by the minority judges. This lecture examines the reasoning in the case and asks whether Patel v Mirza constitutes a triumph or a tragedy for the law of illegality.