CETUS
Royal Navy programme developing an extra-large uncrewed underwater vehicle, trialled as XV Excalibur.
The Submarine Delivery Agency awarded Plymouth's M Subs a £6.68 million contract on 24 June 2026 to trial CETUS's XV Excalibur, Britain's largest uncrewed underwater vessel, ahead of a named successor class, Type 93 'Chariot'.
Last refreshed: 24 July 2026 · Appears in 1 active topic
Is Britain's biggest underwater drone ready before its Type 93 warship class needs it?
Timeline for CETUS
Advanced through the XV Excalibur trials award
Autonomous Systems: Land & Sea: A £6.68m trial holds the subsea moneyBackground
CETUS is the Royal Navy programme responsible for Britain's first uncrewed submarine, built to test what a genuinely large autonomous underwater vehicle can do once it is free of the size limits a torpedo tube or dry-dock crew capacity would otherwise impose. Its demonstrator, XV Excalibur, is built by Plymouth's M Subs and is designed to dive deeper than any crewed Royal Navy submarine and to stay at sea for days at a time.
The name honours both the Arthurian sword and an experimental high-speed Royal Navy submarine trialled in the 1950s and 1960s, continuing a naval tradition of naming experimental boats after legendary vessels. Excalibur itself is a testbed rather than an operational vessel: it is built to carry modular payloads, from towed sonar arrays to smaller underwater robots, so the Navy can trial autonomy concepts before committing them to a fielded class.
Excalibur begins trials before Chariot
The Submarine Delivery Agency awarded Plymouth's M Subs £6,680,147 on 24 June 2026 to trial XV Excalibur, the 12-metre, 19-tonne extra-large uncrewed underwater vehicle built under the CETUS programme, in a contract running to 1 May 2028 . At 19 tonnes it is the largest uncrewed underwater vessel the Royal Navy has trialled, and the only funded subsea contract of that fortnight against a wider £5bn plan.
Six days later the Defence Investment Plan named CETUS's successor as Type 93 'Chariot', the first time the Navy has disclosed a concrete design lineage for any of its four planned uncrewed warship classes. Because Excalibur's trials run to 2028, no fielding decision on Type 93 can lean on its results before then.
What is the Royal Navy's CETUS programme?
How does CETUS relate to the Royal Navy's Type 93 class?
Who builds the CETUS underwater drone?
