It wouldn’t be shocking if, in coming years, attack submarines from the U.S. Navy, Royal Navy and Royal Australian Navy all sailed from the same base just 2,500 miles from the Chinese fleet’s main haunt in the South China Sea.

Australia is moving to acquire nuclear-powered submarines while also expanding a naval base on its northern coast that could shorten the distance the boats might have to sail in order to reach a combat zone.

And now there are signs that American and British subs might join the Aussie boats. It wouldn’t be shocking if, in coming years, attack submarines from the U.S. Navy, Royal Navy and Royal Australian Navy all sailed from the same base just 2,500 miles from the Chinese fleet’s main haunt in the South China Sea.

The RAN already has a base in Darwin, but it’s a small one that at present accommodates just nine small patrol boats. The Australian defense ministry in 2019 launched a $200 million project aimed at expanding the Darwin base with additional fuel storage and another wharf so that it can support large surface vessels and submarines.

Britain’s nuclear-powered submarines are to use Australia as a base so that they can have a more persistent presence in the Indo-Pacific region under plans discussed by ministers.

Senior government sources said that the AUKUS pact could lead to the Royal Navy’s £1.4 billion Astute-class attack submarines undergoing deep maintenance in the region so they can stay deployed for longer rather than returning to the Faslane naval base in Scotland.

The plans would materialise once the Australians start building their own fleet of at least eight nuclear-powered submarines over the coming years with the help of the British and Americans.

The source said that the trilateral pact announced last week “opens up opportunities” for the UK, adding: “You’ve got another base … if you want to have more of a persistent presence you need access to maintenance.”

James Peddell, a former defence technology attaché in Washington with experience in submarine technology, said that a base in Australia could allow UK submarines with conventional weapons to have a permanent presence in the region, and also enable cost-sharing between the allies.