Developments in the energy system are shifting the foundations of energy security in the UK and across the world. Technological advances, alterations to demand patterns, and climate imperatives, combined with geopolitical tensions, mean that the potential causes of a crisis – and how the energy system responds – are changing. New strategies are required for energy sector challenges which threaten to undermine political and geopolitical goals, while new technologies make new approaches possible.This paper looks at the UK’s energy security strategy with respect to the challenges posed by oil and gas dependence, with a particular focus on the latter. It asks what national strategies are deployed, as highlighted during the crisis which followed Russia’s invasion of Ukraine, and the conditions which must be in place for these strategies to be effective. It then explores how these strategies might need to change due to the energy transition.The paper finds that while government documents emphasise the need to reduce dependence on oil and gas for both climate and energy security reasons, treatment of extreme energy prices as an economic shock to be managed outside of the energy system means that ministers and civil servants receive insufficient guidance about which policies should be prioritised to ensure both energy security and decarbonisation over the short, medium and long term.