LONDON – Ever since Winston Churchill coined the phrase in the wake of World War II, politicians have extolled the “special relationship” between the United States and Britain.

Under President Donald Trump’s second administration, Britain will settle for a merely functional relationship with its former colony turned most important ally. As Trump threatens to slap tariffs on America’s neighbors, mulls buying Greenland and suggests the U.S. could “take over” and reconstruct Gaza,Prime Minister Keir Starmer’s government is racing to bolster its diplomatic and economic defenses for a turbulent new transatlantic era.

“We’re in such uncharted waters that anyone who claims to know what in the hell is going on is just lying,” said Kathleen Burk, emeritus professor at University College London and an expert on U.S.-U.K. relations.

High stakes for Britain’s Washington envoy

British officials say Starmer hopes to visit Washington in the coming weeks, but he has yet to receive an invitation from Trump.

In the meantime, a heavy burden rests on Britain’s new ambassador to Washington, Peter Mandelson. A towering figure in Starmer’s Labour Party who served in the governments of former Prime Ministers Tony Blair and Gordon Brown, Mandelson replaces veteran diplomat Karen Pierce, who was widely respected by both Democrats and Republicans in Washington.

It’s rare for a politician, rather than a career civil servant, to be given a key U.K. ambassadorial post. The center-left former lawmaker is not an obvious emissary to the Trump administration. Mandelson once called Trump a “danger to the world” — words he now says were “ill-judged and wrong.”

But some analysts see Mandelson as a canny choice. A controversial figure who twice resigned from government over allegations of financial or ethical impropriety, he has — like Trump — repeatedly bounced back. His mastery of political intrigue brought him the nickname “Prince of Darkness.”

Jill Rutter, a senior fellow at the Institute for Government, said Mandelson is “a considerable political talent” with economic expertise from his time as the EU’s trade commissioner between 2004 and 2008.

“He’s also very comfortable with very rich people,” Rutter said. “He’s very well connected. He will give very classy parties.”

In addition to diplomatic clout, Britain plans to deploy another key asset: the royal family. Trump, whose mother was born on Scotland’s remote Isle of Lewis, owns two Scottish golf courses and is a fan of the royals. He praised the late Queen Elizabeth II, who hosted him at Buckingham Palace during a 2019 state visit, and said he had a “great talk” with Prince William when the two men met in December.

A return visit to the U.K. for Trump, replete with pomp and pageantry, seems likely.

Stuck in the middle with EU

Some politicians on the right of U.K. politics see Trump’s return as an opportunity for deeper U.K.-U.S. trade ties, maybe even a long-elusive free trade agreement.

Talks on a trade deal started after Britain left the European Union in 2020 but foundered on issues including agriculture, with strong opposition in Britain to importing chlorine-rinsed chicken or hormone-treated beef.

A further complication is Starmer’s desire for closer trade with the EU as part of a “reset” with the bloc after years of acrimony over Brexit. Sandwiched between the U.S. and the EU, Britain could face pressure to pick a side.

“Surely the choice is obvious,” Conservative Party lawmaker John Cooper said during a recent debate in Parliament. “Under President Trump, the American eagle is starting to spread its wings. … Europe is fading, with sclerotic growth amid political turmoil.”

But Leslie Vinjamuri, director of the U.S. and the Americas program at the international affairs think-tank Chatham House, said choosing between Europe and America was a “ridiculous proposition.” While the U.S. is Britain’s biggest individual trading partner, half of Britain’s trade is with the 27 EU members.

“They can’t choose,” Vinjamuri said. “At the end of the day, Europe, the U.S. and the U.K. are in this together, and so they have to find different ways of working” together.

Pressure over trade and defense

Trump has already ratcheted up pressure on longstanding allies, announcing he would impose tariffs on all goods from Canada and Mexico, then postponing them after getting pledges from the two counties to beef up border security.

Trump has suggested Britain could escape similar tariffs. “I think that one can be worked out,” he said.

Britain is helped by the fact that, according to official U.S. statistics, the U.S. sells more goods to the UK. than it imports.

Britain is also facing pressure from Trump to increase defense spending. Trump has long questioned the value of NATO and threatened not to defend members of the alliance that fail to meet defense-spending goals.

The president has said NATO countries should spend at least 5% of their income on defense, up from the current 2% target. Britain spends 2.3% of GDP on defense and says it will increase that figure to 2.5%.

“The one thing that the Americans will pay attention to is the defense budget, because Britain started losing leverage with the U. S. when its army and its navy started going down in the 1970s,” Burk said.

Britain is one of the biggest supporters of Ukraine in its war against Russia’s invasion — a war Trump wants to end, on terms that remain unclear. Starmer and his officials hope to press the U.S. government not to abandon Ukraine or back a deal favorable to Russian President Vladimir Putin.

British diplomats and spies are also trying to assess what the new U.S. government means for vital intelligence-sharing. Britain and the U.S. share top-secret intelligence as members of the “Five Eyes” group with Canada, Australia and New Zealand.

U.K. officials were somewhat relieved by the appointment of Secretary of State Marco Rubio, an experienced politician and a known quantity. They have little acquaintance with, and some concerns about, Trump’s nominee for FBI director, Kash Patel, and his pick to oversee national intelligence, Tulsi Gabbard. Gabbard has repeatedly echoed Russian propaganda used to justify the Kremlin’s invasion of Ukraine and in the past opposed a key U.S. surveillance program.

Expect the unexpected

It’s impossible to prepare for everything the next four years could bring.

Rutter said ministers and civil servants need to think about the unthinkable. For instance, what happens if deep cuts to regulation and the machinery of government mean parts of the U.S. start failing?

“When do you start having to give people warnings not to fly to the U.S. because we don’t trust your aviation regulation anymore?” she said.

Vinjamuri said the coming years will test to the limit Britain’s historic strength of quiet diplomacy, “working very pragmatically below the headline to try and get things done.”

“The challenge is, we have some known unknowns, (like) what will happen when it comes to America’s support for Ukraine and for Europe’s security,” she said. “But we have a lot of unknown unknowns, too. And that, I think, is going to be the much trickier part.”