The UK prides itself on its special relationship with the U.S. – and Boris Johnson may now need to develop one with Joe Biden, who has been projected as the 46th President.

With Donald Trump in the White House, the UK prime minister had an ally. Trump had called Johnson a "good man" – even giving him the ultimate compliment of describing him as "Britain's Trump."

But Johnson hasn't yet met Biden, and last year the American said Johnson was a "physical and emotional clone" of Trump – and this time, it wasn't a compliment.

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The UK's biggest priority will be to secure a trade deal with Washington, but it won't be easy.

Biden's Democratic Party is concerned the UK government could jeopardize Northern Ireland's Good Friday peace agreement in its Brexit negotiations.

Former U.S. President Bill Clinton helped to broker that deal, which brought peace to the island after several devastating decades of violence, and Biden has said the agreement must not be a "casualty" of Brexit.

Biden has personal as well as political reasons for maintaining peace: he has Irish roots. In his ancestral hometown of Ballina, locals celebrated the election result.

On Sunday, UK Foreign Secretary Dominic Raab said the EU is also responsible for putting pressure on the Good Friday Agreement.

He said: "We've been very clear, we'll never do anything to put at risk the Good Friday Agreement and we've even said that we would never put any infrastructure at the border between the North and the South and of course if the EU do the same this issue is resolved."

It's expected that Biden would re-engage with America's allies – restoring its traditional relationship with the EU and NATO. The UK hopes that despite Brexit, it won't be left behind.