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A Royal Navy deep sea drone has fired a torpedo for the first time in a major technological breakthrough.
The 40ft-long Excalibur crew-less vessel launched a US warhead in secret trials, copying the capability of more expensive and much larger manned submarines.
The UK-built and battery operated subsurface craft has been in trials since 2025 and though it remains an experimental vessel, in future it could offer vital support to the Navy’s ageing and overworked fleet of nuclear-powered hunter-killer submarines.
As the Mail has previously revealed, there have been times this year when not a single Astute submarine has been on active service due to maintenance issues and crew rotations.
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submarine → see → issues
While working submarines have been conducting the longest patrols in Royal Navy history – in excess of 200 days – to cover for the broken down boats.
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submarines → work → boats
Those exhausted submarines have returned to port with their hulls covered in barnacles from resting on the seabed for lengthy periods.
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hulls → exhaust → periods
While precise details remain classified, the 19-ton Excalibur can dive deeper than larger, manned submarines and can sail from the UK deep into the North Atlantic on a single battery charge.
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Excalibur → remain → charge
So the addition to the fleet of Excalibur, or a crew-less submarine based on its design, cannot come soon enough, according to naval insiders.
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addition → base → insiders
Excalibur is also the largest ‘drone-sub’ ever trialled by the Royal Navy.
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Excalibur → trialle → Navy
Excalibur entered the trials phase of its development in May last year - a development marked by a ceremony at His Majesty's Naval Base (HMNB) Devonport.
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Excalibur → enter → Base
The Royal Navy's remaining fleet of manned submarines have been overwhelmed by a surge in Russian subsurface activity in the North Atlantic.
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fleet → remain → Atlantic
Patrols lasting more than 200 days have become 'the new normal' according to Navy insiders due to submarine shortages.
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Patrols → last → shortages
This Vanguard class vessel returned to port covered in barnacles and slime after spending so long on the ocean floor.
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vessel → return → floor
Discussing last week’s successful trial, a Downing Street spokesman last night described ‘a major advance in the future of submarine technology’.
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spokesman → discuss → technology
The breakthrough will be discussed by UK Prime Minister Andy Burnham and US President Donald Trump in talks in New York this week.
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breakthrough → discuss → York
has not been disclosed but their development is a major boost for UK security including addressing the issue of the strategically vital network of communication and energy cables on the sea bed.
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development → disclose → bed
Those cables have been surveyed by Russian spy ships and submarines and would be vulnerable to attack in a time of warfare.
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cables → survey → warfare
Excalibur could monitor the pipelines.
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Excalibur → monitor → pipelines
The torpedoes, designed as part of the AUKUS submarine programme involving the UK, US and Australia, can target enemy surface and sub-surface vessels.
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torpedoes → design → vessels
Excalibur was designed by maritime engineering company MSubs in Plymouth, Devon, as part of a £6million development contract – a tiny sum in naval engineering.
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Excalibur → design → engineering
Initially the crew-less submarine was designed to carry payloads of equipment thereby creating more breathing space aboard the Royal Navy’s manned hunter-killer and bomber vessels.
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submarine → design → vessels
Excalibur belongs to the Royal Navy’s Fleet Experimentation Squadron.
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Excalibur → belong → Squadron
Over the next two years, Excalibur will carry out further sea trials, helping to accelerate the Royal Navy’s use of advanced technologies.
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Excalibur → carry → technologies
It will help develop a better understanding of the unique challenges that come with operating uncrewed vessels of this size – with the aim of future vessels working alongside crewed platforms.
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vessels → help → platforms
The trials and testing will contribute significantly to the Royal Navy’s constant efforts to remain ahead of potential foes beneath the waves, safeguarding key infrastructure, protecting British and allied ships and submarines and gathering intelligence.
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trials → contribute → intelligence
The Aporia
