First new British warhead since the early nineties advances

Britain's Astraea nuclear-warhead program passed its System Design Review in August 2025, a milestone covering the proposed design and its safety case. Astraea will become the United Kingdom's first new warhead since the early 1990s and is being developed without explosive nuclear testing under the Comprehensive Nuclear-Test-Ban Treaty. It is intended eventually to replace the Mk4A warhead carried on Trident missiles, with work led through the Defence Nuclear Enterprise and long-standing U.S. cooperation. The government plans £15 billion of warhead-program spending from 2025-26 through 2029-30, but operational dates and detailed specifications remain classified.