Heydon was called to the bar in 2023. His practice focuses primarily on competition, consumer, regulatory and commercial proceedings and includes intellectual property and administrative law matters. Before becoming a barrister, Heydon was a Senior Associate in the Competition, Regulation and Trade team at Herbert Smith Freehills in Sydney, where he specialised in competition and regulatory investigations and litigation. He previously worked in the same team in London. Heydon has significant experience acting in cartel, misuse of market power and misleading and deceptive conduct proceedings in the Federal Court and contested merger authorisation matters in the Australian Competition Tribunal. His experience also includes complex multi-party litigation and class actions, having advised on high-value competition and class action proceedings in the English High Court, UK Competition Appeal Tribunal and English Court of Appeal. He has worked across a range of sectors including financial services, energy, communications and healthcare. Prior to practising in the Sydney and London offices of Herbert Smith Freehills, Heydon was an Assistant Director at the Australian Competition and Consumer Commission and is able to draw on this experience when advising regulators and government agencies. Heydon holds a Master of Law (First Class) from the University of Cambridge, which included a specialisation in commercial law.