UK HMS Agamemnon submarine completes its first underwater dive at BAE Barrow yard.

BAE Systems confirmed that HMS Agamemnon, the Royal Navy’s sixth Astute-class submarine, has completed her first dockside underwater dive in Barrow-in-Furness. The successful trial marks a critical step before open-sea testing and entry into active service amid rising Russian naval activity.

The UK Ministry of Defence announced on October 13, 2025, that HMS Agamemnon, the sixth Astute-class attack submarine, has successfully completed her first underwater dive inside the dock at BAE Systems’ Barrow-in-Furness yard. The two-day sequence combined a basin dive with a trim and inclining experiment, including the movement of 16 tonnes of lead to verify stability and center of gravity. The milestone comes three weeks after the boat’s commissioning by His Majesty the King and marks Agamemnon’s transition from build to full power-on trials ahead of sea workups.
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HMS Agamemnon, the Royal Navy’s newest Astute-class attack submarine, combines nuclear endurance with ultra-quiet propulsion, advanced sonar and optronic sensors, and a 38-weapon load of Spearfish torpedoes and Tomahawk Block V missiles, giving it unmatched stealth, range, and strike power beneath the Atlantic (Picture source: BAE Systems).

Built to the Astute baseline, Agamemnon measures 97 meters with a 7,400-tonne submerged displacement, driven by a Rolls-Royce pressurized water reactor and pump-jet propulsion that provide essentially unlimited range and high sustained submerged speed. The design couples acoustic hygiene with a rafted machinery layout and thousands of anechoic tiles to suppress signatures in the North Atlantic’s challenging sound channels. These fundamentals are central to the Royal Navy’s requirement to hold contact on advanced adversary submarines at range and to remain undetected while shadowing or striking.

Sensing and combat systems are the Astute class’s calling card. Agamemnon fields the Thales Sonar 2076 suite with bow, flank and towed arrays, integrated through the Submarine Command System and a resilient combat system network. Instead of a traditional periscope, two Thales CM010 non-hull-penetrating optronic masts provide high-definition day, low-light and thermal imagery while shortening exposure time at periscope depth, improving survivability in contested littorals. These masts also host electronic support measures that expand the submarine’s passive picture, feeding a fused tactical display for the command team.

Six 533 mm tubes support a mixed load of up to 38 weapons, typically Spearfish heavyweight torpedoes and Tomahawk land-attack missiles. The UK is upgrading its Tomahawk inventory to Block V, adding improved navigation, hardened communications and a maritime strike variant that complicates an adversary’s surface calculus well beyond the horizon. In parallel, the Spearfish Mod 1 refresh brings a smarter electronics suite, fiber-optic link and safety improvements, validated in deep-water trials in 2024. Together, these increments preserve reach and lethality as Agamemnon moves toward front-line duty.

Agamemnon’s dive confirmation matters because it proves the integrity of the pressure hull and the fidelity of buoyancy and ballast controls before the boat leaves the yard. The trim and inclining data captured this week will underpin performance envelopes for launch and recovery of weapons, masts and countermeasures, and will be referenced during first-of-class evolutions like emergency blow and under-ice surfacing drills. In practical terms, this is the difference between a submarine built to plan and a warship certified to fight.

London has warned Parliament about stepped-up Russian maritime activity around the UK, while NATO navies have publicly tracked surfaced Russian submarines transiting the Channel and Bay of Biscay. In response, Britain is hardening seabed security and exercising AUKUS undersea capabilities to protect critical cables and energy lines. As the Royal Navy’s newest hunter-killer, Agamemnon will sit at the intersection of deterrence, carrier strike escort, and seabed infrastructure defense, reinforcing the Silent Service’s role across the GIUK gap and into the High North. With the first dive complete, the boat will progress to power range tests and open-water trials before joining the Clyde-based flotilla in company with Astute, Ambush, Artful, Audacious and Anson.