Boris Johnson, who in 2015 said he was “genuinely worried” about Donald Trump becoming president, moved fast following his election to forge close links.

And the prime minister secured a relationship with Trump that eluded his predecessor Theresa May. He now has to perform quite the reverse ferret.

“They call him Britain Trump,” the president once said of Johnson – in praise.

Joe Biden similarly has branded Johnson a “physical and emotional clone” of Trump. It was not a compliment.

Biden’s victory will probably lead to awkward conversations between Whitehall and Washington as the British government tries to cling on to its so-called special relationship with the US.

Johnson steered clear of commenting on the presidential race as the world waited for it to be called, citing diplomatic protocols, but perhaps also hedging his bets. But shortly after Biden was named president-elect, he tweeted: “The US is our most important ally and I look forward to working closely together on our shared priorities, from climate change to trade and security.”

The attempt to build bridges with the incoming administration could be a hard sell. Senior Democrats who worked in the last administration, and could play leading roles in the next one, have long memories. “I’m old enough to remember when Boris Johnson said Obama opposed Brexit because he was Kenyan,” Ben Rhodes, Obama’s former deputy national security advisor tweeted dryly in early October. Tommy Vietor, Obama’s former national security spokesperson, added: “This shapeshifting creep weighs in. We will never forget your racist comments about Obama and slavish devotion to Trump but neat Instagram graphic.”

It could be with that in mind that Johnson also added praise for the incoming vice president Kamala Harris for her “historic achievement” of becoming the first woman, first Black and first south Asian person to hold the job. He tagged her in the tweet just to make sure.

Johnson’s decision to emphasise climate change in his message is also unlikely to be a coincidence. Biden has pledged to return the US to the Paris climate change accord on his first day in office, after Trump pulled out. The United Nations Climate Change Conference (COP26) will take place in November 2021 in Glasgow, a chance for Johnson to find common ground with the new president.

The most pressing matter at hand for the British government is a UK-US trade deal. Trump, who infamously repeatedly falsely claimed that he had predicted the result of the Brexit referendum, was gung-ho about agreeing an “ambitious trade agreement”.

But Biden has been much more lukewarm about the the UK’s decision to leave the EU. He has publicly warned about the impact it could have on peace in the island of Ireland. And he tweeted just one week ago: “We can’t allow the Good Friday Agreement that brought peace to Northern Ireland to become a casualty of Brexit. Any trade deal between the US and UK must be contingent upon respect for the agreement and preventing the return of a hard border. Period.”

A trade deal was also never solely in Trump’s gift to give. The US Congress must sign it off. The Democrats look to have retained control the House of Representatives at this election, and Nancy Pelosi, who leads the party in the House, recently warned there was “absolutely no chance” of a UK-US trade deal should she believe the peace process was at risk.

“The Good Friday Agreement is the bedrock of peace in Northern Ireland and an inspiration for the whole world,” she said in September – repeating a warning she issued on a trip to London in April 2019.

Senator Chris Murphy, the Democrat from Connecticut who sits on the foreign relations committee, told HuffPost UK at the time the UK would have a “tough time” getting any trade deal through Congress.

“The United States has interests that we want to protect throughout the Brexit process, and there is bipartisan consensus against blowing up the Good Friday agreement which has maintained stability in Northern Ireland for over 20 years,” he warned.

For fans of elections, both the next UK general election and the next US presidential election are due in 2024. Keir Starmer, the Labour leader, moved quickly on Saturday to associate himself with Biden’s victory.

“Joe Biden and the Democrats have always shared Labour’s values and the links between our two parties remain strong. I am looking forward to building on this and forging an even stronger relationship between the UK and the USA,” he said. “He ran a campaign on the values that we in the United Kingdom share – decency, integrity, compassion and strength.”

Biden cited Jeremy Corbyn’s loss to Johnson as proof a more centrist candidate was needed to win the White House for the Democrats. Starmer will now no doubt use Biden’s victory as evidence for a more centrist Labour Party. As YouGov’s Marcus Roberts told HuffPost UK, Biden may have offered Starmer a “template” of how to win. “Policy can be radical if the candidate is reassuring,” Roberts predicted.

Biden has been running for president since 1988. His attempt to win the nomination that year imploded after he was found to have plagiarised a speech from then Labour leader Neil Kinnock. 

In an interview with Times Radio on Saturday, Kinnock said he was “ecstatic″ about Biden’s win. “The sigh of relief in the United Kingdom is good enough to blow us in the mid-Atlantic,” he said.

🇺🇸 Running Mate is a US election podcast – just for Brits. Now available everywhere.