Stuart O’Brien is a partner at the pensions specialist law firm Sackers, with over 20 years' experience advising on pensions legal issues. He is an authority and regular speaker on trustee fiduciary duties and ESG. At Sackers, he has guided trustee boards of all sizes in understanding their legal responsibilities, particularly in relation to ESG and the integration of climate-related risks in investment decisions.

Stuart has previously chaired the cross-government and industry group – the Pensions Climate Risk Industry Group, providing early guidance in 2021 to trustees on managing and reporting climate-related risks. Most recently, he and fellow Sackers partner Andy Lewis were part of the Financial Markets Law Committee (FMLC) working group, which provided guidance in 2024 on pension fund trustees and fiduciary duties, focusing on sustainability and climate change. Following this work on the FMLC guidance, Andy and Stuart have been instrumental in supporting a cross-industry initiative to bring legislative clarity to the consideration of system-level climate risks as part of trustee fiduciary duties. Stuart is also an active member of the Investment and Defined Contribution Sub-Committee of the Association of Pensions Lawyers.