Royal Navy unveils XV Excalibur: pioneering step in autonomous underwater warfare

In a ceremony held on May 15, 2025, at His Majesty’s Naval Base Devonport, the Royal Navy officially unveiled its first Extra-Large Uncrewed Underwater Vehicle (XLUUV), named XV Excalibur. This marks a significant milestone in the UK’s maritime defense capabilities, introducing a new era of autonomous underwater operations.

Developed under the three-year Project CETUS, XV Excalibur is a 12-meter-long, 2.2-meter-wide vessel displacing 19 tonnes, making it the largest uncrewed submarine trialed by the Royal Navy to date. Built by Plymouth-based MSubs, the submarine is designed to operate autonomously for extended periods, conducting missions such as intelligence gathering, surveillance, and reconnaissance in contested environments.

The naming ceremony was attended by 200 guests, including Rear Admiral James Parkin, Navy Director Develop, representatives from AUKUS nations, naval trainees, and cadets. Honorary Captain Peaches Golding OBE CStJ RNR, the Lord Lieutenant of Bristol, christened the vessel in traditional naval fashion with a bottle of Plymouth Gin.

Over the next two years, XV Excalibur will undergo extensive sea trials as part of the Royal Navy’s Fleet Experimentation Squadron, under the Disruptive Capabilities and Technologies Office. These trials aim to enhance the Navy’s understanding of operating large uncrewed vessels and integrating them with crewed platforms. The vessel’s modular design allows for the testing of various payloads, contributing to the development of future naval strategies.

Rear Admiral Parkin emphasized the significance of this development, stating, “In our journey towards autonomy and mass, it is vital we learn by doing, and Excalibur will be our mechanism for understanding the complexity and challenges of operating a future team of crewed and uncrewed vessels and systems underwater.”

The introduction of XV Excalibur represents a strategic advancement in the Royal Navy’s capabilities, positioning the UK at the forefront of autonomous underwater warfare technology.