AUKUS Submarines: Steel in 2027, Numbers in 2028, and an Astute Gap Britain Cannot Afford

By Mark Allatt, UK Defence First

Five years after AUKUS was announced, the partnership is no longer a press-release abstraction. Australia is building yards, hosting allied boats and training a nuclear workforce. Britain has confirmed that steel will be cut on the first SSN-AUKUS attack submarine at Barrow in 2027. Yet the same official update postpones a decision on how many boats the Royal Navy will buy until 2028. For UK Defence First, that sequence is the wrong way round. First steel is welcome. Waiting two years to confirm fleet size, while the Astute class ages towards decommissioning, is not.

Australia is moving from concept to concrete

The Australian side of Pillar I is now visible on the ground. The Australian Submarine Agency, created in 2023, has shifted from institution-building to delivery. At HMAS Stirling, Australia has completed successive submarine maintenance periods: USS Hawaii in 2024, USS Vermont in 2025, and HMS Anson in 2026 - the first such work on a Royal Navy nuclear-powered submarine on Australian soil. Those visits are rehearsals for Submarine Rotational Force-West, due to begin in 2027 with up to four United States boats and one British boat rotating through Western Australia. In South Australia, the Nuclear-Powered Submarine Construction Yard at Osborne is taking shape, backed by investment now totalling some A$8.5 billion. Construction of the first Australian-built SSN-AUKUS is planned by the end of this decade, with the first boat due in the early 2040s.

This is not yet a fleet. The Optimal Pathway still depends on three Virginia-class transfers in the early 2030s, and American yards have not reached the two-boats-a-year rate that pathway assumed. Even so, Canberra has done the unglamorous work: steel-supply qualification, combat-system partnerships, workforce pipelines and the 50-year Geelong Treaty with Britain. Australia is treating nuclear propulsion as a national project. Britain is treating the size of its own successor fleet as a decision that can wait.

Steel next year, service in the late 2030s

The Defence Nuclear Enterprise update of September 2026 is the clearest official statement of the British programme in a year. On current plans, steel will be cut on the first UK SSN-AUKUS in 2027. Contracts worth around £4 billion have already been placed. The first Royal Navy boat is still planned to enter service only in the late 2030s. Construction will take place at BAE Systems in Barrow. Reactors for British and Australian boats will be built at Rolls-Royce Submarines in Derby, supported by Australia’s £2.4 billion contribution over ten years. Ministers still speak of a drumbeat of one attack submarine every 18 months and of “up to 12” boats.

Those are serious industrial commitments. They are not a force structure. Cutting steel on a first-of-class boat while the total order remains unconfirmed is an odd way to run a programme that must also compete with Dreadnought at the same yard and reactor works. Detailed design continues through 2028. First-of-class risk will sit on both sides of the Indian Ocean at once: Barrow will find the faults, while Osborne is expected to build in parallel rather than after a proven lead ship.

Numbers delayed until 2028

The Strategic Defence Review of 2025 and the Defence Investment Plan recommitted the government to “up to 12” SSN-AUKUS boats. That phrase has been hollowed out. Ministers now say exact hull numbers need not be settled until the design phase ends in 2028. The already-late Investment Plan did not settle the question. Britain will therefore start cutting steel a year before it says how many hulls it intends to fund. In the 1990s the Royal Navy had 18 SSNs in service in addition to a number of older SSKs which were briefly replaced by the four (of a planned 12) Upholder-class SSKs which were prematurely sold to Canada.

Industry cannot tool, hire or lock a supply chain on an “up to”. Continuous production only works if the order book is real. A yard asked to deliver an 18-month cadence after decades of stop-start Astute construction needs certainty, not a holding line. If London will not say how many boats it will take for itself, it is harder to insist that Barrow and Derby serve a coherent Allied plan rather than a sequence of announcements.

The Astute clock is already running

This would matter less if the existing attack flotilla had spare life. It does not. HMS Astute commissioned in 2010 against a design life of roughly 25 years. She entered her first mid-life revalidation period at Devonport in 2025 and will be unavailable for years. Later boats will hit the same wall through the 2030s and early 2040s. The seventh and final Astute, HMS Achilles, has slipped towards 2028 or 2029. The class will have taken close to 28 years from first keel to last delivery. Availability in 2025–26 has been grim: boats alongside for lack of docks, spare parts and people, with at least one hull used as a donor for others. Sending HMS Anson to Australia was a necessary AUKUS signal. It was also a reminder that the Royal Navy is already stretching a thin force.

On present plans the first SSN-AUKUS arrives in the late 2030s - at best as Astute herself approaches the end of a hard-worked life, and more likely as a replacement rather than an addition. If the lead boat takes anything like the Astute first-of-class interval from steel-cut to service, “late 2030s” is an optimistic reading of 2027. Subsequent boats at an 18-month drumbeat would not restore a seven-boat force, let alone grow it towards twelve, before older Astutes leave the line. Life-extension can buy time only by consuming docks, crews and money the nuclear enterprise already lacks. Unless the whole programme is accelerated - earlier follow-on boats, a firm order above replacement level, and infrastructure treated as a warfighting priority - Britain will face a gap between the boats it has and the boats it has promised.

UK Defence First, not AUKUS later

AUKUS is in Britain’s interest. A common design, shared reactors and an Australian contribution to Derby strengthen the base on which the deterrent and the attack flotilla both depend. None of that excuses a timetable in which Australia’s effort looks more urgent than the replacement of the Royal Navy’s own hunter-killers.

UK Defence First has argued that Britain must be able to act alone, supply its own forces and keep a continuous production drumbeat for nuclear submarines. That requires a confirmed SSN-AUKUS fleet large enough for the North Atlantic, carrier-group protection and an Allied presence East of Suez without cannibalising hulls. Twelve was the right ambition. Leaving the number until 2028, after first steel, repeats the old habit of announcing a class and discovering the quantity later. The threat in the North Atlantic will not wait. Neither will the Astute out-of-service dates.

Steel in 2027 is a start. It is not a strategy. Confirm the numbers now, accelerate the build, and put the Royal Navy’s replacement fleet ahead of every presentational milestone. Otherwise Britain will enter the 2040s with a partnership celebrated in three capitals and too few attack submarines of its own.