Britain, France, and Germany are edging closer to what has been dubbed a “strategic triangle” after a series of meetings and agreements this month.
Sir Keir held meetings, first with French president Emmanuel Macron , and then with German chancellor Friedrich Merz , in London, after which treaties were signed.
The prime minister hosted both leaders to get relations moving on the back of a few rocky years following Brexit.
Although Sir Keir has appeared keen to play up the anti-immigration gang elements of the deals, the agreements will also help speed up passage for visitors.
Here is what the agreements have contained.
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What has Britain signed with France?
Mr Macron was treated to a three day visit in London and the French president was seen to embrace his opposite number when he arrived.
The visit carried a certain pomp with it being the first state welcome given to a European leader since Brexit.
The headline announcement was the one in, one out migrant deal aimed at deterring small boat crossings over the Channel, more than 20,000 of which have been made already this year.
Under the terms, France will take back asylum seekers who cannot prove a family connection to the UK. But for each migrant the French take in, the UK will grant asylum to one from France.
Sir Keir said: “We all agree that the situation in the Channel cannot go on as it is so we’re bringing new tactics into play and a new intent to tackle illegal migration and break the business model of the criminal gangs.”
Both countries have previously blamed each other over the crisis and have said they are working hard to discourage crossings, and sort through case files.
Action groups have complained that the deal is “side stepping” the issue .
Dr Razia Shariff, the chief executive of Kent Refugee Action Network (Kran) said: "There's a little bit of light if you like, given the fact that they are going to be offering some safer legal routes on this new scheme, but it's definitely not enough. It's a drop in the ocean, right?"
What has Britain signed with Germany?
The so-called Kensington Treaty, named after where it was signed, is the first post-war agreement between the two countries.
After meeting Mr Merz, Sir Keir once more put the immigration issue central to the outcome.
The prime minister tweeted: “Germany has committed to change their law so we can disrupt the supply of small boats.
“Working with our international partners gets results for British people. We will smash the people smuggling gangs and secure our borders.”
In addition, the agreement has secured:
Sir Keir added: “I've been very concerned about the fact that engines, in particular, but component parts of the boats that are being used are travelling through and being stored in Germany, but they can't be seized because the law didn't accommodate for a country which had left the EU and therefore needed to be amended.
"And I am very grateful for the chancellor, and we've discussed this at great length on a number of occasions, he's now going to change the law, introduce the necessary legislation, so that we can intervene in that place."
