In late June 2026, the Royal Navy revealed a troubling situation: all five of its active Astute-class submarines were docked at port, unable to perform their duties. The Ministry of Defence does not share current submarine readiness levels beyond August 6, and no official statement has confirmed a full recovery. The active submarines in the fleet are HMS Astute, Ambush, Artful, Audacious, and Anson.
HMNB Devonport is the primary site for nuclear-submarine maintenance in the UK. By June 2026, the country had only three operational nuclear-certified docks. No. 9 Dock was occupied by a Vanguard-class submarine undergoing a lengthy refit, No. 15 was holding HMS Audacious, and No. 10 Dock was in the midst of a £750 million redevelopment, expected to finish in 2027. HMS Astute was waiting for a dry dock, while other submarines faced extended delays.
Challenges in Maintenance Capacity
Vanguard-class submarines, responsible for maintaining Britain's nuclear deterrent, receive priority access to docks, engineers, and maintenance teams. The Defence Committee discovered that some submarines had waited over two years for maintenance due to limited facilities and staff shortages. In a 2026 report, the committee warned that this strain could hinder British military commitments in the Euro-Atlantic and Indo-Pacific regions.
The Times reported that more than £500 million in submarine maintenance work has been delayed since 2018. In 2023-24, £650 million of this budget was actually spent, highlighting a gap between planned and executed maintenance.
The problem is not limited to a single issue. It stems from a small fleet, too few nuclear-certified docks, missed maintenance, a lack of trained workers, and thin spare-parts inventories. These challenges are compounded by the government’s focus on the nuclear deterrent, which takes precedence over conventional submarine support.
Impact of Limited Dock Availability
HMS Astute was docked in Devonport in June 2025 for a midlife refit expected to last several years. It waited for a dry dock due to the limited availability. This practice, while keeping some boats functional, left Ambush in a weakened state.
HMS Artful had not been to sea since around May 2023, and HMS Audacious had been in Devonport since April 2023, waiting for a dock spot for nearly 22 months before finally entering No.
Each submarine in the fleet has faced its own set of maintenance challenges, and their issues are converging to create a major readiness problem.
The last Trafalgar-class submarine retired in December 2024, removing any remaining buffer in the fleet. With just five Astute-class boats in operation, the impact of one being in a long refit is significant. This situation removes 20 percent of the fleet before accounting for unexpected defects, training, and overseas missions.
Operational and Strategic Implications
The small number of boats contrasts with the highly advanced capabilities of the Astute-class submarines. They are designed for tasks such as protecting Vanguard submarines, hunting hostile boats, gathering intelligence, and supporting carrier groups.
The workforce and spare-parts issue also contributes to the problem. Devonport and Faslane require nuclear-qualified engineers, welders, inspectors, planners, and safety personnel. These specialists must work with low-volume components for submarines built over decades.
The decision to use parts from HMS Ambush to support other submarines highlights the strain on the fleet. This practice helps keep one boat operational but weakens the donor submarine's ability to return to service. Long periods in port also reduce the experience of crews, affecting command and sonar operations essential for mission success.
The government acknowledges that the pressure on the fleet reflects years of underinvestment in submarine dock infrastructure. The current situation has led to missed deployments and increased stress on an already limited number of submarines. Addressing these issues will require significant investment in facilities, workforce training, and supply chain improvements.
