“Hi, I’m the new guy,” said the newly installed American official who will be the country’s face to the outside world, as he greeted his new staff one morning last week. What he didn’t add was that he also may well be taking on the toughest job in town.

Even the Senate confirmation of Rex Tillerson as Secretary of State was messy. Personally I found Tillerson one of the more reassuring Trump appointments. Sure, he had no conventional diplomatic experience. But for the last 10 years he has run ExxonMobil, the West’s largest oil company, often described as “a state within the state” that operated on six continents, and dealt on a daily basis with government and business leaders around the world. As a qualification for high level diplomacy, that isn’t bad.

Yes, his past cosiness with the Putin regime in Russia was worrying. But another business leader, George Shultz under Ronald Reagan, had been a pretty competent Secretary of State. Tillerson had the stuff to do the same. And I know these things shouldn’t matter, but he looks like a Secretary of State too.

The controversial orders Donald Trump has already issued Show all 9 1 /9 The controversial orders Donald Trump has already issued The controversial orders Donald Trump has already issued Trump and the media White House Press Secretary Sean Spicer takes questions during the daily press briefing Getty Images The controversial orders Donald Trump has already issued Trump and the Trans-Pacific Partnership Union leaders applaud US President Donald Trump for signing an executive order withdrawing the US from the Trans-Pacific Partnership negotiations during a meeting in the Roosevelt Room of the White House in Washington DC. Mr Trump issued a presidential memorandum in January announcing that the US would withdraw from the trade deal Getty The controversial orders Donald Trump has already issued Trump and the Mexico wall A US Border Patrol vehicle sits waiting for illegal immigrants at a fence opening near the US-Mexico border near McAllen, Texas. The number of incoming immigrants has surged ahead of the upcoming Presidential inauguration of Donald Trump, who has pledged to build a wall along the US-Mexico border. A signature campaign promise, Mr Trump outlined his intention to build a border wall on the US-Mexico border days after taking office Getty Images The controversial orders Donald Trump has already issued Trump and abortion US President Donald Trump signs an executive order as Chief of Staff Reince Priebus looks on in the Oval Office of the White House. Mr Trump reinstated a ban on American financial aide being granted to non-governmental organizations that provide abortion counseling, provide abortion referrals, or advocate for abortion access outside of the United States Getty Images The controversial orders Donald Trump has already issued Trump and the Dakota Access pipeline Opponents of the Keystone XL and Dakota Access pipelines hold a rally as they protest US President Donald Trump's executive orders advancing their construction, at Columbus Circle in New York. US President Donald Trump signed executive orders reviving the construction of two controversial oil pipelines, but said the projects would be subject to renegotiation Getty Images The controversial orders Donald Trump has already issued Trump and 'Obamacare' Nancy Pelosi who is the minority leader of the House of Representatives speaks beside House Democrats at an event to protect the Affordable Care Act in Los Angeles, California. US President Donald Trump's effort to make good on his campaign promise to repeal and replace the healthcare law failed when Republicans failed to get enough votes. Mr Trump has promised to revisit the matter Getty Images The controversial orders Donald Trump has already issued Donald Trump and 'sanctuary cities' US President Donald Trump signed an executive order in January threatening to pull funding for so-called "sanctuary cities" if they do not comply with federal immigration law AP The controversial orders Donald Trump has already issued Trump and the travel ban US President Donald Trump has attempted twice to restrict travel into the United States from several predominantly Muslim countries. The first attempt, in February, was met with swift opposition from protesters who flocked to airports around the country. That travel ban was later blocked by the Ninth Circuit Court of Appeals. The second ban was blocked by a federal judge a day before it was scheduled to be implemented in mid-March SANDY HUFFAKER/AFP/Getty Images The controversial orders Donald Trump has already issued Trump and climate change US President Donald Trump sought to dismantle several of his predecessor's actions on climate change in March. His order instructed the Environmental Protection Agency to reevaluate the Clean Power Plan, which would cap power plant emissions Shannon Stapleton/Reuters

Nonetheless the Senate only approved him by 56 votes to 43, virtually along party lines. It was the narrowest passage of any Secretary of State in modern times – even Condoleezza Rice won 85 “Yes” votes in 2005, at the height of the unpopularity of the Iraq war of which she had been one of the architects.

But that vote may only be the start of it. Tillerson is taking charge of a department in turmoil, whose morale is on the floor. The Trump era began with a rash of high level forced resignations, a haemorrhage of institutional wisdom. That was quickly followed by the debacle of the edict banning refugees from various Muslim countries, on which the State Department was not consulted, even thought it would perforce be closely involved in its implementation.

That in turn prompted an unprecedented 1,000 State employees to register their disagreement through the department’s established “dissent channel”, arguing the order was not only against core American values but likely to be counterproductive as well. And the response? A sneering White House spokesman who described the signatories – the country’s eyes and ears to the outside world – as “career bureaucrats”, and told them either to “get with the programme” or be gone.

Restoring the department’s morale and sense of purpose is Tillerson’s first task. However, a second and far more important one is to ensure his own and State’s clout within the administration, at a moment when conventional diplomacy seems anathema to the new president.

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Up to a point, the problem is not new. In recent times, the White House, whether in Democrat or Republican hands, has gathered the reins of foreign policy making ever more tightly. Colin Powell was greeted like a rock star at the State Department when he became Secretary in 2001. But he lost out in one turf battle after another with the Pentagon and the White House.

Hillary Clinton was another highly popular Secretary of State, with a profile if anything higher than Powell’s. But on the big issues – Iraq, Afghanistan and, above all, Syria – boss Barack Obama called the shots. But the Trump White House is another beast entirely.

It is run by a president who is an instinctive authoritarian, who finds himself in the perfect position to indulge his bullying habit, happy to upset allies as readily as foes. Egging him on (some would say calling the shots) is his top adviser Steve Bannon, alt-right iconoclast and scourge of the status quo, and current runaway leader in the “who’s the power behind the throne in the White House” guessing game that unfolds at the start of every new administration.

The hit list of these last few days is pretty impressive. A telephone row with the prime minister of Australia, loyal friend of the US for generations. A stormy conversation with the prime minister of Mexico, America’s key hemispheric partner, in which Trump threatened to send US troops to Mexico to get rid of the “bad hombres” (only joking, the White House said later).

Germany and Japan, both vital allies, have been flatly accused of currency manipulation. The EU meanwhile describes Trump as a “dangerous challenge” to the bloc, right up there with Russia, China and radical Islam. The notion is incredible. But it’s true. We may be witnessing an assault on an entire world order in place for more than half a century.

So where will Tillerson fit into all this? Will he emerge as a policy shaper and a Trump-tamer, or merely act as pooper-scooper for the diplomatic messes the 45th president leaves blithely in his wake, reassuring slighted or nervous allies that Trump doesn’t really mean it (even though every sign is that he does)?

And although Tillerson is a businessman, will he and the State Department accept this White House’s concept of foreign policy as purely transactional, as if international relations were a zero sum game, in which one side’s gain is automatically the other’s loss?

A couple of litmus tests are already at hand. Wearing his ExxonMobil hat, Tillerson opposed sanctions on Russia. But at his confirmation hearings he took a tougher line on the Kremlin’s behaviour in Crimea and eastern Ukraine. Now, in his first weekend in office, he must confront what look like deliberate tests by Vladimir Putin of what he can get away with, now the US has a president whose admiration for him seemingly knows no bounds: the renewed Russian-inspired fighting near Donetsk, and the apparent repeat poisoning of the opposition leader Vladimir Kara-Murza.