While firm-level Environmental, Social, and Governance engagement (ESG or usually termed Micro Stewardship) can influence individual companies, research shows this level of engagement is insufficient when market and system-level incentives reward unsustainable behaviour. This research explores how financial professionals drive system-level change through Macro Stewardship - an advocacy program that aims to engage policymakers, regulators, and standard-setters to reshape the financial system in favour of sustainable practices. The study explores the central question: How can a committed group of industry insiders catalyse system-level change from within? Specifically, it investigates (1) why and how an embedded team instigates a movement toward sustainable finance, (2) the tensions between insider and social advocacy roles, and (3) the impact of their efforts.

Using non-market strategy and social movement theory as the lens, the research analyses how these actors frame issues, build alliances, mobilise resources, and navigate institutional constraints to influence policy and regulation. The findings suggests that system-level change may be correlated to combining insider access with broader stakeholder mobilisation.

The thesis concludes by introducing the two tools for industry practitioners, developed by the author: the Institutional Macro Stewardship Adoption Framework (IMSAF) and the Insider Stewardship Flywheel (ISF). These tools arise directly from the research questions and findings. IMSAF addresses why and how an embedded team can initiate a movement toward sustainable finance by outlining the capabilities required.  ISF, in turn, captures the action cycle through which these capabilities translate into framing, coalition-building, agenda-setting, and ultimately policy influence. Together, the two tools reflect the study’s core insight that system-level change emerges from the interaction between internal organisational conditions and strategic external action, offering a structured way to understand, and potentially replicate, how industry insiders catalyse change from within.