Con Coughlin:

Mrs May needs to back the US against Syria and Russia if she wants to be the first person Trump calls

There will have been more than a few anxious moments in Whitehall when it emerged that the first Western leader Donald Trump contacted when weighing up Washington’s response to the Syrian crisis was the French president, Emmanuel Macron. Ever since the end of the Cold War, it has been an article of faith of the transatlantic partnership that, when dealing with an international crisis, the first country the White House turns to is Britain.

Kuwait, Bosnia, Kosovo, Iraq, Afghanistan and, more recently, the campaign to defeat Islamic State of Iraq and the Levant (Isil). In each instance, it has been Britain that has – to use Tony Blair’s phrase – stood “shoulder to shoulder” with Washington. Other key allies, such as France, Germany and Canada, have generally had to play second fiddle. Yet on this occasion Mr Trump, when considering his response to further accusations that Syrian dictator Bashar al-assad is using chemical weapons against his own people, has broken with this long-standing tradition.

There is nothing wrong, per se, with Mr Trump making Paris his first diplomatic port of call. France is one of our closest allies in the realms of defence and security cooperation and – after a few initial misgivings – recently joined the mass expulsion of Russian diplomats over the Salisbury poisonings.

Even so, there will have been a degree of disquiet in Downing Street that Mr Trump’s instinct was to turn first to Mr Macron, rather than the Prime Minister, Theresa May. In the feverish world of international diplomacy, such perceived slights can have profound outcomes. David Cameron’s decision to overthrow Libyan dictator Muammar Gaddafi in 2011 is said, in part, to have been motivated by his desire not to be outmanoeuvred in Washington by France’s then president, Nicolas Sarkozy.

Mrs May, too, will be keen to ensure that it is Britain, not France, that assumes the primus inter pares role among Washington’s allies in dealing with Syria, particularly as it was just a few weeks ago that Washington demonstrated its unwavering support for the UK by carrying out, in response to the Salisbury attack, its largest mass expulsion of Russian diplomats since the end of the Cold War.

If Mrs May, though, is serious about maintaining Britain’s pre-eminence in Washington, she needs to demonstrate that, this time around, Britain is an ally that can be trusted to deliver, and not let the Americans down – which is what happened the last time London was asked to intervene militarily against the Assad regime.

I refer, of course, to the disastrous 2013 Commons vote, when Mr Cameron failed to persuade MPS to allow him to join the Obama administration in bombing Assad’s forces. One factor in the vote’s outcome was the mess Mr Cameron’s Libyan campaign had made of that country.

Mr Trump says he is fond of Britain, the country of his mother’s birth, and has even offered to help secure us a favourable post-brexit trade deal. But he does not have the temperament of man who is going to hang around on an important issue like Syria while Downing Street dithers over supporting military action.

So, in terms of reasserting Britain’s position as a major global player, this is, in a very real sense, make-orbreak time for Mrs May. Either she demonstrates her commitment to the transatlantic alliance by offering Washington military support, or she ducks the issue and indulges in the same political cowardice as Mr Cameron in 2013 by insisting that she must first secure Commons backing when, as most parliamentary experts will tell you, no such requirement exists in the British constitution.

Nor, while we are on the subject of sticking with the Americans, is Syria the only issue where Downing Street needs to show some solidarity.

Last week the US imposed wide-ranging sanctions against various Russian oligarchs, including Oleg Deripaska, the erstwhile holiday companion of George Osborne and Peter Mandelson. The sanctions were imposed in retaliation for Russian meddling in the US elections, as well as its illegal annexation of Crimea.

And yet, despite the unequivocal backing Britain received from Washington over the Salisbury attack, Britain has so far done nothing to support the American stance. On the contrary, it has allowed Mr Deripaska to float one of his companies, EN+, on the London Stock Exchange. The flotation, moreover, enjoyed the backing of businessmen with impeccable Tory credentials.

Lord Barker of Battle, the chairman of EN+, is a former Tory minister, while the PR campaign was handled by Finsbury, whose chairman is none other than Roland Rudd, the brother of the current Home Secretary, Amber Rudd.

If this is the thanks Washington gets then the Americans might be tempted to rethink their priorities in the transatlantic relationship. And they may well conclude that, in any future crisis, their interests are better served by once again making Paris, not London, their first port of call. FOLLOW Con Coughlin on Twitter @concoughlin; READ MORE at telegraph.co.uk/opinion