The UK Supreme Court recently handed down its hotly-anticipated judgment in the business interruption insurance test case (FCA v Arch and others [2021] UKSC 1). The judgment extends, in certain respects, findings in favour of certain policyholders of business interruption insurance made by the High Court. In this client alert, Jumana Rahman, Thomas Shortland, and Charlotte Ritchie focus on the implications of the Supreme Court judgment for causation issues in insurance law and the wider law and address the consequences of the judgment for various key stakeholders.