Progressively, Donald Trump redrafts the rules of statecraft

The sign outside the main gates of Wellington Barracks proclaims the message: “Open. Please Visit.” Tourists duly wander to the Georgian building from Buckingham Palace across the road.

But while the visitors from around the world are very welcome, there is one guest that the soldiers in the barracks are unlikely to see anytime soon. Donald Trump. The elite infantry and cavalry divisions that provide the escort and the bands for state visits have been stood down after petitions and threats of demonstrations prompted a rethink of an invitation to Mr Trump.

With its “special relationship” with the United States, Britain prides itself on standing top of the list for overseas visits by the most powerful man in the world.

The opportunity had already been and gone when Mr Trump made a highly-consequential visit to Saudi Arabia, the Middle East and a series of European summits in May.

To the quiet chagrin of its diplomats, Britain won’t even hold the first bilateral European trip by the US leader.

Mr Trump spent part of last week in Poland before he moved on to Germany, where he was the focus of protests by anti-capitalist anarchists.

The real sore point for the British is yet to come. On Friday, Mr Trump returns to Europe to be feted amid the pomp and splendour of the French national day, Bastille Day.

It is the breastplates of the French Republican Guard that will bob to the trot in front of Mr Trump as he views the parade and flypast. The ceremony and the mood of national relaxation should serve as an antidote to attempts to drum up disruptive and violent protests such as those at the G20 gatherings this weekend.

The Paris images should play well on American television screens. Emmanuel Macron, the new French leader, is certainly keen to show that he can handle Mr Trump. At the G7 in Sicily, his aides gleefully briefed that the 39-year old had crushed the US leader’s hand. The US president has a grip-and-pull handshake that is designed to show who is boss. The diminutive Mr Macron was determined not to lose out.

It is a tribute to Mr Macron’s quick thinking that he seized on Bastille Day as a platform for wooing Mr Trump. That is not a gamble open to Theresa May, the British prime minister. There is no British equivalent to the republican holiday in France and the febrile mood in London means there would be large-scale clashes.

Mr Trump assured Mrs May that he would be visiting London when they met in Hamburg, yesterday but the trip, formerly scheduled for the autumn, could be delayed to 2018.

Which leaves one question. Does it matter that the US president hasn’t displayed his affinity in person?

This is a president that doesn’t set much store by the rulebook of statecraft. While he visibly enjoyed the elaborate celebrations in Riyadh in May, his visit had real substance, too. He gave important backing to the counter-extremism agenda, a legacy that will be long-lasting.

By contrast, his days in Europe appear to be a chore. The US leader does not set much store in the honeyed praise his hosts offer in podium speeches nor does he give ground to their anguished pleas for a change in policy behind closed doors.

He has followed his America First agenda at all his stops. Mr Trump bluntly admonished the Europeans for not spending enough on defence. To stoke jitters, he refrained from a blanket reiteration of the Nato article 5 mutual defence pact. He rebuffed all calls to stay in the Paris climate change accord at G7 and was unbending on calls for a rethink last week in Hamburg. Nor did Mr Trump pay much heed to warnings about tariff wars as result of his trade policy.

It is hard to see Mr Macron making a breakthrough with the American president. After all, Europe is already protectionist with its internal market regulations and heavy subsidies. America is merely threatening to up its game to European levels.

While Mr Trump is denounced for his migrant-bashing, Eastern European states are building walls on their borders to stop the flow. Liberals jeered at his warning that western civilisation was endangered but many Europeans nodded along.

In the politics of summitry and state visits, there is what is apparent and that which is really dictating events. For all their troubles, the British can take comfort that the US president shares an Anglo-centric outlook. It doesn’t take a state visit to Britain to show off his sympathy.  After all, it was Mrs May who made it through the White House portals to visit him first.

The display on the Champs Elysee on Friday is certain to jar British nerves, but the show of friendship can be seen another way: fake news.

Meanwhile, the regiments of Guards and the Household Cavalry in the grand barracks of central London wait for the order to polish their boots.