Theresa May worked her magic on Donald Trump but he could turn against her in an instant

He was clearly hugely impressed by Theresa May and, for once, this normally boastful, often insulting, and occasionally threatening man could hardly have been warmer and more friendly. The Prime Minister had certainly worked her magic on him.

And in addition to the touching hand-holding episode, he praised Brexit as “wonderful”, predicted the relationship with Mrs May would be even stronger than that between Margaret Thatcher and Ronald Reagan, and vowed that so long as he is President, the special relationship between the US and the UK would remain as firm as ever, with regular trade deals advantageous to both sides.

His compliments could hardly have been more fulsome. Yet they should come with a “health warning”: Donald Trump has shown himself to be a man who, at the drop of a hat, will change his mind and go, as it were, into reverse gear.

He is on record as having said things and then later contradicting them without the turn of a hair. So, his gushing compliments over the weekend could, according to those who know Donald Trump, be forgotten about and those warm feelings be replaced by far colder ones.

Indeed, no sooner had the Prime Minister left the US than Trump’s highly controversial crackdown on migration came into force. The Prime Minister, through Downing Street, has said she is against this policy and that if a Briton got caught up in it, there could be repercussions.

So, if you are wise, you take Trump’s words with a pinch of salt.

• While Theresa May was basking in her White House triumph, Jeremy Corbyn was suffering all kinds of humiliation as, according to one disillusioned Labour Party member, he was leading Labour to the grave.

A little overdramatic perhaps, but the truth is that under Corbyn’s stewardship, Labour has never been in such a mess.

His order, in the form of a three-line whip, that Labour should support the Bill in the Commons enabling the Government to start getting to grips with Brexit, has led to yet more resignations from the shadow cabinet and is being defied by a number of Labour back-benchers as well. In short, party discipline no longer exists.

A substantial number of Labour MPs want Corbyn to quit as leader but, try as they might, they find it impossible to get rid of him. The Parliamentary Labour Party is far and away the most important component of the party (although the union bosses don’t think so), yet they are stuck with him.

And unless someone gets a grip of the party’s internal rules and changes them, Labour will surely continue on this downward spiral to the grave.

They have been warned.

• Tam Dalyell, the ex-Labour MP who died last week aged 84, was an example to many MPs who cynically believe that back-benchers are virtually impotent, except for providing lobby fodder for their party leaders.

He belonged to the “drone until they drop” school of politicians, but was proud to be tedious. “I make no apology for boring the pants off everyone,” he once said. It was by this method of constant repetition that he usually achieved his objective.

Oddly, dogs have figured in his career. Once, after knocking on doors in his Linlithgow constituency, he was telephoned by a local councillor. Dalyell told him that one woman had complained about dog mess. The councillor told him abruptly: ‘Westminster’s your business. Dog sh*t’s mine’, and slammed the phone down. Tam never again interfered in local politics.

He had an odd effect on dogs. Twice, during election campaigns he was seen running, in panic and in an ungainly fashion, down the street with growling dogs in hot pursuit.

And during his national service, he once achieved what no other squaddie had done before or since: He lost a huge armoured vehicle on Salisbury Plain, something which would defy even the most brilliant illusionist.

“I was never cut out to be a soldier,” he said. “I was the despair of every sergeant major I encountered.”

His running feud with Margaret Thatcher, particularly over the sinking of the General Belgrano during the Falklands conflict, is well documented. He called her “a liar” and worse, and was ejected from the Commons when he refused to withdraw the epithets.

Later he was invited to a dinner at a Central American ambassador’s residence. The only two guests without partners were Dalyell and Thatcher. He was compelled to link arms with her and escort her to the table, where, during the meal, they engaged in highly forced and insincere small talk with each other. It must have been galling for them both.

But Dalyell was the most honest, honourable, straightforward, non-spinning MP I encountered in all my years in the Commons.

• How come President Trump, who professes an obsession about germs, and usually refuses to shake hands with people for that reason, finds it possible, and probably pleasant, to hold the hand of Theresa May during her White House visit?

The answer is probably obvious, but it does demonstrate an inconsistency in the President’s make-up.

The belated excuse provided by White House officials that he grabbed her hand because he is afraid of steps, does not, I am afraid, ring true to me. But then I was always a romantic.