HMS Anson's arrival at HMAS Stirling in February 2026 represented a watershed moment for Australian defence planning. The UK's Astute-class nuclear submarine completed an 8,200 nautical mile non-stop transit from Gibraltar, marking the first time a British nuclear-powered submarine has undergone maintenance outside UK waters. The strategic implications are significant: Australia is now demonstrating it can service the advanced technology it will eventually build and operate.
Over several weeks, 100 personnel from the Royal Australian Navy, Royal Navy, UK Submarine Delivery Agency, and US Navy worked on HMS Anson's hydraulic systems, in-water engineering, and emergency response exercises. Two RAN officers embedded aboard the submarine gained operational experience on a working nuclear vessel. This was no ceremonial visit. The maintenance work directly builds the technical knowledge and supply chains Australia will need when construction of its first SSN-AUKUS submarine begins at ASC's Adelaide facility late this decade.
Yet this operational milestone obscures a troubling strategic reality. Australia confronts a severe capability gap that no amount of partnership goodwill can easily resolve. The Collins-class submarines, which have served Australia since the 1990s, are scheduled to retire from 2038 onwards. The first Australian-built AUKUS submarine will not arrive until the early 2040s. That gap of several years creates a period when Australia's undersea deterrent capacity will be severely diminished, potentially at a time when Indo-Pacific security is anything but stable.
The problem extends beyond timing. Full-cycle maintenance of Collins-class boats already takes longer than planned, with each life extension overhaul consuming more than two years due to age-related technical risks. Availability is falling. When Australia eventually fields eight AUKUS submarines, defence planners project only two will be deployable at any given time. By 2056, assuming the programme stays on schedule, Australia will have a smaller effective force than it does today.
AUKUS partner nations face their own constraints. In late 2025, the UK Royal Navy experienced periods when it had no single Astute-class submarine at sea, a concerning indicator of capacity limitations among Australia's closest allies. The sustainment demands of a fleet of eight nuclear boats would likely exceed the combined effort required to build the original Collins-class and maintain it for 30 years. This is not a problem that can be solved through goodwill visits or expanded maintenance facilities alone.
From a national security perspective, Australia is making the right long-term strategic choice with AUKUS. The capability gap, however, means the next decade will test Australian defence planning in ways that demand honest discussion and careful prioritisation of allied resources. HMS Anson's successful visit demonstrates AUKUS partners can work together operationally. Whether they can sustain that partnership through a transition period of unprecedented complexity remains an open question.