It’s been a big day for Australia–UK relations. Sandwiched between the release of the ‘refresh’ of the integrated review in London and the AUKUS submarine announcement in San Diego, a bilateral partnership growing in warmth and strategic significance is evident, and indeed flourishing.

That the two developments take place in the Euro-Atlantic and Indo-Pacific chimes with the British conception of a merging between the two geostrategic areas. The integrated review refresh christens the emergence of an ‘Atlantic–Pacific’ theatre.

That Australia occupies such a significant place in Britain’s refresh is indicative of the new thinking in London. Australia is the second most referenced Indo-Pacific partner in the document behind the US, the UK’s closest and most powerful ally.

It wasn’t always this way. Despite their oft-cited shared history and worldview, Australia and the UK diverged throughout much of the Cold War era as the UK doubled down on containing the Soviet threat. However, it’s now clear that the deteriorating geopolitical environment—characterised by Russia’s war against Ukraine in the Euro-Atlantic and especially China’s increasing assertiveness in the Indo-Pacific—is drawing them back together.

In this sense, Australia is said to be integral to the UK’s ‘new network of “Atlantic–Pacific” partnerships’ that enables and buttresses its ability to ‘shape the international environment’ to uphold an open international order. Shaping the international order is now the central goal of UK foreign policy.

Today’s AUKUS announcements best encapsulate this. British and American nuclear-powered attack submarines (SSNs) will now be forward-deployed to Fleet Base West in Western Australia ‘as early as 2027’—a quick win for AUKUS that will enhance the efforts of both the US and UK in maintaining a stable Indo-Pacific and equipping the Royal Australian Navy with the necessary know-how to operate SSNs. Australia is expected to acquire a minimum of three and maximum of five Virginia-class submarines from the US to undertake patrols until a more permanent arrangement can be implemented.

This more permanent arrangement will involve Australia’s buying into the UK’s program to build the Royal Navy’s next generation of SSNs, which are already being described as ‘SSN AUKUS’. They will be based on the UK design and kitted out with technology from all three nations, notably America’s high-end weapons capabilities. Britain will build the first vessels for the Royal Navy in Cumbria at its Barrow-and-Furness site sometime in the late 2030s. Australian SSN AUKUS boats are projected to be in the water by the early 2040s, with the first being assembled in Adelaide.

This is significant for the UK not least because it will reinvigorate the British defence-industrial base, particularly its naval shipyards in Cumbria. Creating a larger class of SSNs should also enhance economies of scale for both nations. Ben Wallace, the UK defence secretary, has already declared that the number of personnel at the site will increase 10,000 to 17,000, a significant boost to meet the new demand.

The evident strategic (re)convergence between Australia and Britain can also help provide answers to some of the questions still surrounding AUKUS.

With its Indo-Pacific overseas territories, France is the only European partner—albeit behind Britain—with the capacity to meaningfully project force into the Indo-Pacific. This makes it the European Union’s only true Indo-Pacific power, and one that Australia will want to engage with. The extraordinary reaction of France to the initial AUKUS announcement is a well-told story; though Anthony Albanese, Australia’s prime minister, attempted to smooth things over in July last year, relations between the two countries still remain fuzzy.

Again, enter Britain. On 10 March, the UK–France summit was held for the first time in five years, and the two powers discussed how to combine their efforts to ‘ensure permanent presence of like-minded European partners [in the Indo-Pacific]’. France is clearly eager to deepen its involvement in the Indo-Pacific’s security architecture, and the UK—as the European power most embedded in it—is keen to draw France in. No longer so much ‘down under’ as ‘top centre’, Australia will remain critical to France, irrespective of AUKUS, if Paris is to secure its own regional interests. The thaw in French–UK relations can only be good for Australia.

But there are also lessons the UK can learn from Australia. Although the initial AUKUS announcement may have been difficult without the veil of secrecy, Canberra has clearly adjusted its diplomacy and messaging to the Indo-Pacific. Albanese and his cabinet have kept in close contact with regional partners, and he will visit Fiji on his way back from San Diego. If London wants to shape the international order and foster closer relations with so-called middle-ground countries in the developing world, the UK will need to moderate its language and keep an ear to the ground on regional sensitivities.

In a single day, Britain and Australia, together with the US, have put in place the foundations for a partnership that will last at least 50 years. This new centre of geopolitical gravity binds the three together and to the Indo-Pacific region. With resolution and careful diplomacy, they can foster an Indo-Pacific that is ‘open, stable, prosperous and respectful of sovereignty, human rights and international law’.