The British military has a long-established, albeit often debated, role in domestic affairs, primarily through Military Aid to Civil Authorities (MACA) under the Civil Contingencies Act 2004. This framework outlines military support for civil authorities during natural disasters, network disruptions, and even criminal activity, with civil primacy always maintained. This chapter examines the British armed forces’ unprecedented peacetime domestic operation in response to the COVID-19 pandemic, the largest domestic deployment in British peacetime history. Their diverse roles included manufacturing and distributing PPE, constructing temporary NHS hospitals, pioneering mobile testing units, providing logistical and planning expertise, and assisting with the rollout of vaccines. While demonstrating the military’s immense utility and adaptability, Operation Rescript also highlighted critical issues in civil-military relations. Concerns arose regarding the potential for military overstretch, its impact on combat effectiveness, and the "securitization" of the pandemic through governmental language and military involvement. The experience underscored the need to balance domestic support with core defence responsibilities, especially given recent force reductions and heightened geopolitical tensions.