The 'doctrine of equivalents' (ie, the principle that a patent may be infringed by a product or process which is considered equivalent to that protected by the granted patent) was not historically adopted by the UK courts. It arrived in UK patent law only following the landmark Supreme Court decision in <i>Actavis UK v Eli Lilly</i> in 2017. Now, four years on from that decision, this article considers the post-<i>Actavis</i> development of the doctrine, recent trends and implications for litigants in the United Kingdom.