The Submarine Delivery Agency (SDA) has formally handed over the experimental vessel XV Excalibur to the Royal Navy, marking a significant step in the UK’s development of autonomous underwater systems.
The vessel, the largest uncrewed submarine ever operated by the service, is the culmination of Project Cetus, a joint initiative between the SDA and Plymouth-based MSubs Ltd. Developed in under three years, the project serves as a key testbed for assessing military payloads and establishing operational trust in autonomous technology, presenting future opportunities for suppliers in the sector.
Designated as an Extra-Large Uncrewed Underwater Vehicle (XLUUV), the 12-metre, 19-tonne submarine has successfully completed a series of demanding acceptance trials since its launch in February 2025. Following its official naming ceremony at HMNB Devonport in May, the vessel will now undergo a comprehensive two-year test and evaluation programme with the Royal Navy, which will inform future requirements and operational concepts for autonomous platforms. The SDA’s Autonomy Unit will continue to provide support throughout this phase, aiming to identify effective pathways for integrating autonomy into frontline service.
Recent trials have already demonstrated the platform’s advanced capabilities and the critical role of the UK supply chain. During Exercise Talisman Sabre in August, as part of the AUKUS Pillar 2 advanced capability workstream, the Royal Navy successfully controlled Excalibur in UK waters from a remote operating centre in Australia. This exercise proved the system’s long-distance interoperability and showcased UK-Australia collaboration.
Furthermore, the vessel completed a world-first trial by operating at sea with a quantum optical atomic clock developed by UK-based company Infleqtion. This technology is vital for enhancing navigation and timing accuracy without reliance on GPS, enabling prolonged and covert submerged operations. The successful integration of this system, delivered six months ahead of schedule, highlights opportunities for specialist technology firms to contribute to major defence programmes.
© Crown Copyright / © MOD
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Post written by: Christian Doak
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