This submission to the House of Commons Defence Committee addresses the potential role of civilian nuclear facilities as radiological weapons for an enemy of the UK. The submission does not purport to provide a thorough analysis, but rather to bring a neglected subject to the Committee’s attention. The report describes relevant nuclear facilities, citing the B215 facility at Sellafield as an example. It relates how a nuclear facility can be used as a weapon and the effects of a radioactive release. It then explains our present understanding of the threat and how it can be addressed, concluding with recommendations to the Committee.