In his first days as tore up a to deport asylum seekers to Rwanda and spoke to his Ukrainian counterpart to ensure rock-solid support in the war with Russia.
The UK's new Labour government is expected to be "hawkish" in supporting Ukraine, trying to move closer to Europe and moving on from the Conservatives' .
Russia won't be happy with the change in leadership but Australia has reason to be, experts say.
Here's what the new government means for the rest of the world.
What can we expect from UK immigration policy?
Labour have formerly been seen as soft on immigration but they will want to be seen as mostly keeping the status quo, politics and international relations researcher at Macquarie University Tom Howe told SBS News.
Reform UK promises to stand up for "British culture, identity and values" and in particular targets immigration, which it blames for many economic and social issues.
Starmer had promised to cancel the Rwanda scheme before he was elected, and has said he will curb the number of immigrants arriving to England by boat from France by hiring specialist investigators and using counter-terror powers to "smash the criminal gangs", but how this will work in practice remains largely unknown.
"The Rwanda scheme was dead and buried before it started," Starmer said in his first press conference on Saturday.
"It's never acted as a deterrent. Almost the opposite."
No asylum seeker has been deported under the Rwanda scheme, described by critics as an "Alice in Wonderland adventure that was both absurd and inhumane".
Scores of people, reportedly as many as 200, who were due to be deported have recently been released on bail by immigration judges because there was no longer a realistic prospect of removal within a reasonable timescale.
Who is the UK's new foreign minister?
David Lammy, the son of Guyanese immigrants, represents an inner-London constituency and has spent much of his political career campaigning for social and racial justice.
He travelled to Germany shortly after being appointed as foreign minister to seek to build stronger ties with European economies.
"Let us put the Brexit years behind us ... there's much that we can do together," Lammy said, pointing to a previously floated idea of a UK-EU security pact.
David Lammy was sworn in as the UK's new minister for foreign affairs. Source: AAP / Thomas Krych/AP
"They talk about wanting to improve relations with Europe, but the Europeans don't really want to do that. The trade cooperation agreement works pretty well for Europe. They aren't really incentivised to reword that in any meaningful way and Europe has its own challenges now."
Lammy is also seeking to push for a ceasefire in Gaza, and build ties with Donald Trump's Republican Party.
Lammy has also flagged the UK could be looking to shift its relationships with some of the countries it had colonised, professor of international relations at Griffith University Ian Hall told SBS News.
"One of the first things Lammy said as foreign minister is 'I'm the descendant of enslaved people'. And so he wants to say, 'Look, we've got to address these kinds of issues, these historical issues, but also Britain needs to reconnect with the global south.'
Hall said the overarching theme of the new Labour government will be "security, security, security."
What does the change in government mean for Australia?
Historically the UK Labour Party and the Australian Labor Party have run on similar policy platforms and shared advisers, and so may have a closer relationship with Australia than that of the Conservatives, Howe said.
However, if the UK is focusing much of its military efforts in Europe, that could raise questions on how committed it is to the Indo-Pacific, Hall said.
"There's been a lot of discussion saying that the UK needs to diplomatically engage in support of the rules-based order in the Indo-Pacific. So you might see more diplomatic engagement and less defence engagement, but that might be good for Australia," if it meant the UK was prioritising diplomacy over ships and aircraft in the region, he said.
The Labour Party has said it remains committed to the .
What about Russia and Ukraine?
The UK has been one of Ukraine's biggest supporters and Starmer's first phone call was to Ukrainian President Volodymyr Zelenskyy.
This was a clear message to the world, Hall said, and "Russia is not going to be happy".
"The Labor Party under Starmer has been very clear in its support for Ukraine and very critical of Russia. So this is not a result that Russia will welcome."
Howe said the UK would continue to be as "hawkish" against Russia as it had been during the Cold War era.
The UK is one of the leading donors to Ukraine, alongside the US and Germany. The UK has pledged £12.5 billion ($23.7 billion) in support to Ukraine since February 2022.
On the other hand, Farage has been somewhat "pro-Putin", Howe said, which could create an interesting wedge in British politics if any of his statements gain traction.
With additional reporting by AAP and Reuters.
