Oodles of diplomatic energy have been expended on the unlikely relationship between the former human rights lawyer, Sir Keir Starmer and the former real estate magnate turned reality TV star, Donald Trump.

It was a political double act that long appeared unlikely and, for a while at least, appeared much stronger than many would have anticipated.

It doesn't look quite so strong any more, after President Trump belittled and mocked the Prime Minister publicly, comparing him, deeply unfavourably, with the UK's most celebrated wartime leader, Winston Churchill.

But hang on a second. It is worth seeing all this with some historical context.

It was Churchill, after all, who first talked 80 years ago this week of the so-called "special relationship" between the UK and America.

America currently has a president whose language and outlook can change in minutes, so it is worth thinking of this outburst in the context of an international dynamic with decades of contemporary history.

The relationship ebbs and flows depending on the personalities and politics of those in Downing Street and the White House.

Folk I've spoken to in the security services say in their world, it really is a special relationship – the connections are deep, with staff embedded in each other's countries and institutions.

But in the political world, it does wax and wane.

History reminds us big stand offs between London and Washington, such as the UK resisting American pressure to send troops to Vietnam, don't have to banish relations to a perpetual deep freeze.

It is also true that President Trump's deeply personal remarks have the capacity to wind and wound.

Downing Street had worked so hard and invested so much in building a decent working relationship with President Trump. It is just six months ago that he was here in the UK enjoying a second state visit. There was a lavish state banquet and compliments lavished by both men on each another. And look where things are now.

No 10 is not shooting its mouth off in public in reply, but folk I speak to in government are resolute.

They express a pride in what they believe was the prime minister acting in the national interest, doing what they think was both lawful and right and they point to early evidence that suggests British public opinion is on their side.

A YouGov poll suggested America's initial strikes were unpopular in the UK.

Precedent suggests too a big blow-up with President Trump doesn't necessarily mean the relationship is doomed – things can blow over.

But after all the effort invested into building up this relationship, it has never been in a rockier place than it is now. (BBC)

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