Donald Trump’s second instinct was the right one, while – surprise, surprise – his first was not. And, as ever, it is those initial blunderings, grotesque and self-serving, that we’ll remember. And they tell us a lot about the man and how his empathy-depleted, self-serving mind works.

So we can dispense with Step Two quickly. He phones Theresa May and extends condolences and a hand of cooperation in the wake of the Parsons Green train attack. Well done Donald – that wasn’t so hard. Civil exchanges of mutual support between leaders can matter in times of national shock, and both Britain and the US are doing plenty behind the scenes on terror.

Step One, cock-eyed and deplorable, came via Twitter. The panic on the tracks is barely over and Trump trots out four tweets, all unhelpful. To what end did he imply, for instance, that the London police had screwed up because the perpetrators were already known to them? These, he said, were “sick and demented people who were in the sights of Scotland Yard”. Is that so? Was he guessing or did he have classified information, and if so why was he blabbing about it?

Forensics officers investigate the scene (AFP/Getty) (AFP)

The Prime Minister, of course, has been criticised for being mealy-mouthed in the past each time Trump has overstepped the boundaries of decency, most recently with his attempts to say that the counter-protestors and the white supremacists equally shared the blame for the mayhem – and murder – in Charlottesville last month.

This time, she rebuked the president rather swiftly. If she hadn’t, maybe he wouldn’t have bothered placing that call to her subsequently.

“I never think it’s helpful for anybody to speculate on what is an ongoing investigation,” she said after a meeting with her top domestic security experts. The Metropolitan Police weren’t amused either. The comments were counterproductive and “pure speculation”, it said in a statement.

That Trump is madly inconsistent barely needs pointing out. It’s about what suits him at the time. When he was assailed for his initial comments on Charlottesville, he said he hadn’t wanted to say anything more – blame the haters – before having all the facts.

“When I make a statement, I like to be correct,” he said. “I want the facts ... I don’t want to rush into a statement.” Does he not see how ridiculous that sounds? Coming from him. Juxtapose that with his Friday tweets and you might laugh. Or cry.

On the first day of June, many in Manila were startled when Trump lamented they too had becomes victims of terror. “Pretty sad what is going on throughout the world with terror,” he said. “Our thoughts and our prayers are with all of those affected.” Except that what he assumed was a terror attack was one man trying to rob gamblers in a casino. He’d jumped the gun.

Two days after Manila, the savagery at London Bridge unfolded. There was no mistaking what that was about. Yet Trump managed to anger everyone in the capital by willfully twisting a statement from Mayor Sadiq Khan urging Londoners not to be alarmed by all the armed officers on the streets. Trump inferred he had said they shouldn’t be alarmed by the attack itself.

Theresa May on Trump's Parsons Green response: "I never think it's helpful to speculate"

That was not helpful, and plainly dishonest. Except each time this happens, Trump thinks he is being helpful – to himself. He uses each tragedy to inflate himself or prove a point. He tried to manipulate the 2015 Paris massacres to bolster his campaign trail argument that gun control was making America less safe.

He used Paris, in fact, as a told-you-so moment – never mind the obscenely misguided logic. “This message is repugnant in its lack of any human decency. Vulture,” French ambassador to the US Gerard Araud replied.

Told you so was also the message from Trump on Friday. This is why we need the travel ban I have talked about so often and the courts keep thwarting me on. He was basically saying, I am right, you see. No one else understands what we must do to protect our citizens. And it’s why political correctness is such a mistake.

Actually, it was more complicated. Recently, Trump has alienated much of his base by seeming ready to renege on a promise to deport 700,000 Dreamers, young people brought illegally into the country when they were kids, and by cosying up with Democrats in Congress. This was a wink to say he hasn’t forgotten about them – he is still their tough guy on terror and immigration.

Restaurant owner hands out free pizza at Parsons Green

“Must be proactive & nasty,” he wrote. “Loser terrorists must be dealt with in a much tougher manner. The internet is their main recruitment tool which we must cut off & use better!”

The notion of shutting down the internet to frustrate Isis and other terror networks was first raised by Trump in late 2015, at the same campaign event that saw him calling for a “total and complete shutdown of Muslims entering the United States”.

Trump was using the pain of those fleeing the flash of fire on the District Line to rebalance his political fortunes at home. Cynical politics, indeed. And his conservative fans should know by now not to put any store in his immigration promises. The Supreme Court is due to rule on the constitutionality of his 90-day travel ban on visitors from Iran, Libya, Somalia, Sudan, Syria and Yemen on 10 October. And the ban will expire on the last day of September anyway.