The Royal Navy has proudly unveiled the XV Excalibur, Europe’s largest unmanned submarine ever built, reinforcing its leading role in autonomous submarine technology. The launch ceremony, held on 15 May 2025 at the South Yard of HMNB Devonport Naval Base in Plymouth, heralded a new era in submarine technology. Measuring 12 metres in length and displacing 19 tonnes, the experimental platform is the Royal Navy’s largest unmanned submarine to date.
The Flagship of the CETUS Project: The Development Process of XV Excalibur
XV Excalibur is a product of Project CETUS, a project launched in 2022 by the Royal Navy’s autonomy and innovation teams, in close collaboration with industry partners and the Defence Equipment and Support Agency (DE&S). The groundbreaking submarine was built in Plymouth by UK-based MSubs and was launched for the first time at Turnchapel Wharf in February. Following delivery, it underwent a range of port and sea trials at Devonport Base, where its operational capabilities were rigorously assessed.
Loyalty to a Historical Submarine: The Naming Ceremony and Its Symbolic Meaning
The submarine was named in a traditional ceremony, with the symbolic naming of its hull by the Lord Representative of Bristol, Honorary Captain Peaches Golding OBE CStJ RNR, by breaking a bottle of Plymouth gin. The name ‘Excalibur’ was chosen in reference to a historic British submarine that entered service with the Royal Navy in 1947 and where the high-test peroxide (HTP) propulsion system was tested. This meaningful name choice combines both respect for the past and an innovative vision for the future.
High-Level Participation and the Strategic Importance of Autonomous Submarines
The launch ceremony was attended by Rear Admiral James Parkin, Director of Development, Royal Navy, representatives from AUKUS (the security alliance between Australia, the United Kingdom and the United States), cadets and around 200 other guests. This high-profile participation clearly demonstrates the strategic importance of integrating autonomous submarines into the UK Navy. As underwater warfare and the protection of critical undersea infrastructure become increasingly vital, unmanned submarine technologies have the potential to offer a significant advantage in this area.
XV Excalibur's Mission: Intelligence, Surveillance and Reconnaissance
Not directly designed for operational missions, XV Excalibur will serve as part of the newly established Fleet Experimental Team. This experimental platform will provide critical data for the development and implementation of future autonomous submarine technologies. XV Excalibur will be used for intelligence gathering, surveillance and reconnaissance missions in close collaboration with the Royal Navy’s experimental ship XV Patrick Blackett. These missions are vital to understanding the potential use and effectiveness of unmanned submarines.
Modular Design and Long Range Operation Capability
Despite being smaller in size than traditional manned submarines, the XV Excalibur’s modular structure gives it the ability to successfully perform long-range surveillance missions and operate in restricted areas. This capability suggests that unmanned submarines could offer a significant advantage in scenarios where manned platforms would be risky or operationally challenging.
Rear Admiral Parkin’s Emphasis: Combining Manned and Unmanned Systems
Speaking at the launch ceremony of the XV Excalibur, Rear Admiral James Parkin, Director of Development, Royal Navy, emphasised that the platform will provide an important testbed for how manned and unmanned submarine systems can be used together in the future. This approach demonstrates that future naval operations will be complex and multi-dimensional, and therefore it will be critical for platforms with different capabilities to work synergistically. The data to be gained from the XV Excalibur will play a key role in shaping the Royal Navy’s future submarine strategies.
As a result, the Royal Navy’s introduction of the XV Excalibur is a monumental step forward in autonomous submarine technology in Europe. This innovative platform has the potential to significantly enhance the UK Navy’s underwater capabilities and is expected to play a key role in future maritime security strategies. The experiences and technological advances that will be gained from the XV Excalibur will inform the future of autonomous submarine technology, not just for the UK but for navies around the world.
