He specialises in contentious regulatory work and has very extensive experience of acting for financial institutions in high profile, complex regulatory investigations, both domestically and cross-border. He also has experience of acting for institutions in Serious Fraud Office investigations. 

Calum has advised major financial institutions across a very broad range of regulatory issues, including market abuse and insider dealing, AML and anti-bribery and corruption, mis-selling, fraud, cyber security breaches, operational resilience, non-financial misconduct and other cultural issues, regulatory reporting and a broad range of other types of systems and controls failings. He also represents senior individuals in regulatory investigations. 

Calum has advised extensively on the UK Senior Managers and Certification regime and on related FCA and PRA Code of Conduct and fitness and propriety issues. 

Legal directories recognise Calum as a leading individual for contentious regulatory matters. Chambers UK 2024 states that "Calum is the best regulatory lawyer I have dealt with in the City; his advice is clear and succinct and his judgement is spot on. He is a trusted adviser." He has "a lot of experience and industry knowledge, and is able to smoothly run complex and large investigations".