Public sector information and communication technologies (ICT) cost taxpayers in the United Kingdom (UK) over £16 billion annually and are responsible for between 35-38% of ICT-related Greenhouse Gas (GHG) emissions. While the UK's Greening Government ICT Strategy is regarded as an exemplar in regard to the latter, the Government ICT Strategy addresses the former in terms of eliminating the unnecessary proliferation of ICT applications and infrastructures that resulted from recent e-Government and Transformational Government strategies. Thus, given the crisis in public finances, the Government ICT Strategy aims to reduce ICT-related costs and to improve service delivery, while reducing GHG emissions. This paper's field study of the UK government's ICT strategies draws upon institutional theory for its mechanism-based conceptual framework. The findings of this study delineate the institutional mechanisms that underpin strategy implementation and enable the attainment of strategic objectives. While the study has several significant implications for research and practice, one notable finding is that contrary to the 'iron law' of climate policy, the UK government's focus on ICT-enabled GHG emissions reductions did not diminish with the economic downturn, as the cost savings associated with the introduction of efficient, Green ICT provided sufficient justification for the required infrastructure investment.