UK and Australia Sign Long-Term Pact to Build Nuclear Submarines

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The United Kingdom and Australia have signed a fifty-year defence agreement to collaborate on SSN-AUKUS nuclear-powered attack submarines under the AUKUS security partnership. Known as the Geelong Treaty, this pact is regarded as among the most significant defence collaborations between the two nations in decades.

It was signed on 26 July 2025 in Geelong, Victoria, by UK Defence Secretary John Healey and Australian Defence Minister Richard Marles, formalising their long‑term commitment to SSN‑AUKUS submarine cooperation. The SSN-UKUS submarines will be powered by British-designed Rolls‑Royce nuclear propulsion systems, with construction using shipyards and workforces in both the UK and Australia.

The treaty outlines cooperation on design, construction, sustainment, operation and eventual disposal, alongside workforce training, infrastructure development and regulatory alignment under AUKUS Pillar I. It also enables rotational deployments of UK Astute‑class submarines to HMAS Stirling in Australia under the Submarine Rotational Force-West initiative, enhancing strategic presence in the Indo‑Pacific.

The deal is forecast to generate up to £20 billion in UK exports over 25 years and support more than 21,000 high-skilled jobs across the submarine industrial base and supply chain. The agreement is seen as a substantial boost to Britain’s defence and shipbuilding sectors, reinforcing domestic industrial capacity at a time when revitalising manufacturing is a government priority.

Strategically, the treaty underpins AUKUS Pillar I cooperation between the UK, Australia and the United States, intended to strengthen deterrence amid rising security tensions in the Indo‑Pacific. It also reflects the UK’s deeper engagement with Pacific allies and its expanding strategic posture beyond Europe.

While the United States is conducting a review of AUKUS under President Donald Trump’s administration, both UK and Australian officials have expressed confidence in the pact’s long‑term continuation. They have portrayed the Geelong Treaty as a foundational measure cushioning the alliance against uncertainties in U.S. foreign policy direction.

The submarines will use Rolls‑Royce nuclear propulsion technology. UK construction is set to begin at Barrow‑in‑Furness, while Australian work will take place in Adelaide’s Osborne yard, drawing on combined industrial expertise.

Beyond procurement, the agreement signifies deepening bilateral trust, economic partnership, and a shared commitment to regional stability. Amid escalating Indo-Pacific tensions, the two nations are positioning themselves to confront future security challenges while reinforcing domestic industrial resilience.