Suddenly, I find myself wondering if this is about to be a Zelensky moment. I am in the Oval Office at the White House to present President Donald Trump with a copy of my new biography, Elizabeth II. 

Whereupon the most powerful man in the world starts flicking through the index to look up a few of the things I have said about him. The silence around the room is deafening.

'Let's try this page,' he says. I pray it's not one of those about Nato. He turns to a section on the late Queen's sang-froid under fire. 

In it, I have noted that she – like the President and also King Charles, Ronald Reagan and Pope John Paul II – are members of that exclusive club of world leaders who have survived being shot at in public.

It is, of course, a particularly sensitive subject after last Saturday's assassination attempt on the President at the Washington Hilton. The President nods – 'that's nice,' he murmurs – and moves on.

He is tickled by another chapter in which I have pointed out that he was Elizabeth II's last State Visitor when he arrived at the Palace in 2019 (Covid and health issues precluded any more). 

'I was the last? I hope I didn't do anything to offend her!' he joked. I pointed out that she had found him, according to those close to her, 'charming, tall, tanned, big, courteous, mid-century' and also 'amusing'.

'I've had better,' he smiles adding, 'and I've certainly had worse.'

It's late in the day and I am the last visitor on the President's schedule. But he is in exuberant form, clearly buoyed by the success of this week's state visit of the King and Queen who will be saying farewell in the morning.

'We've done a good job with the King, right?' he says. I reply that the British team seem overjoyed by the success of this trip.

'He's a great guy, he really is,' he says, adding warm tributes to the Prince and Princess of Wales. He is less complimentary about the Sussexes.

I am entirely aware, of course, that I am only here because of the President's deep-rooted fondness for the Royal Family. 

It's the reason why he agreed to see me four months ago when I flew to Mar-a-Lago to interview him for my book. 

And it's the only reason that I have been allowed into the Oval Office to give him a first copy of the US edition.

I had been due to see him over the weekend but the shooting at the White House Correspondents' Dinner had torn up the schedule and I imagined that the moment had passed. 

However, as I am going to the airport to leave Washington, word comes through that I should head for the White House at the end of the day. 

The cancelled appointment would be honoured after all. Courteous indeed, as the late Queen noted.

After extensive security checks, I am escorted into the private lobby of the West Wing, the atmosphere calm, purposeful and quiet. 

Famous faces come and go. Treasury Secretary Scott Bessent strides in, chats to another familiar face, and strides on.

The walls are lined with landscapes and also a dramatic scene from the opening action of the War of 1812 against the Brits – a sea battle between HMS Belvidera and a squadron of US warships. Apparently, it was a gift from Winston Churchill.

While I wait, I am escorted to see two fascinating sights, the Cabinet Room and the Roosevelt conference room, each with a single chair two inches taller than all the others. It all feels surprisingly intimate, even more so, in fact, than No 10 Downing Street.

Finally, I am summoned to the Outer Office of the Oval Office and then told to walk right on in. 

'Just what I need. A book on the Queen!' declares the President in mock exasperation. He is on his feet and beckoning me over to the famous Resolute Desk, the gift from Queen Victoria which now constitutes the epicentre of Western power.

He is alert, ebullient, chatty, even at the end of a full day. A quartet of aides are there too. I pass him my book but he wants to check it out before holding it up in front of the White House photographer. 

'Let's see if he's said reasonably nice things…' he murmurs.

The President spots my photograph of the last portrait ever painted of Elizabeth II. She sat for the artist, Basia Hamilton, in the last months of her life. 

He had just acquired a copy of the original when I went to see him in Florida. 'It's a beautiful picture, isn't it. And it's hanging there at Mar-a-Lago,' he says proudly.

Satisfied that this is not a demolition job on either the late Queen or himself, he gives the photographer the nod.

Talk turns to his fondness for his royal visitors and he checks his schedule for the official departure the following day when the King and Queen will head on to Virginia and thence back over the Atlantic.

'It's been unbelievable,' he reflects, before asking after the Prince and Princess of Wales. 'William, he'll be a good King, won't he?' he says. 'He's very nice. A great guy. I like him.' 

I observe that one of the Prince's key priorities is not just his role as heir to the Throne but that of ensuring the next royal generation want to embrace their destiny. 'The kids are good kids, right?' he nods.

'So can Harry make a comeback?' he asks. I say that any return to the royal fold is looking highly unlikely. 

'Too many things, I guess,' he sighs. 'That wife of his. Boy, what she's done to that guy.' 

I say that the couple were clearly unhappy with the royal hierarchy. 'I guess she got blocked out by William's wife,' the President continued, as he reflected on the 'perfect' performance of the Princess of Wales. 

'How's she doing? She's so great. She was sick, people said crazy things about her and she was so brave.'

He starts to go through the book again as he looks again at the title – and points to the 'II' after 'Elizabeth'. 'Did you see that woman the other day who thought 'II' was eleven?' he exclaims and the whole room bursts out laughing. 

'That was a killer!' He is referring to the Democrat Congresswoman Ilhan Omar, an ardent anti-Trumper, who managed to read out a speech citing 'World War Eleven'. 'Queen Elizabeth the Eleventh!' he chuckles.

Finally, he reaches into a drawer of the Resolute Desk. He pulls out a magnificent souvenir replica of his presidential seal and hands it to me, along with a White House pen. He wishes me well with the biography. 

'If I like a book, it's a bestseller,' he adds earnestly. I recall the story he told me in Florida about his former doctor, James Jones, being bitten by a lethal viper in Peru. 

Jones wrote a subsequent memoir which the President had endorsed and the book flew off the shelves.

I head off into the evening drizzle and finally arrive at the airport. As I am checking in, a friend sends me a message asking if I have seen the President's social media post on Truth Social. 

I assume he means the message from earlier in the week when Mr Trump posted my Daily Mail article revealing his ancestral link to a Scottish nobleman, making him a 15th cousin of the King. But it's not that one.

'Robert Hardman has written an amazing book about the incredible life of the beloved and deeply respected Queen Elizabeth II,' the President writes to his umpteen million followers, adding that 'Elizabeth II. In Private. In Public. Her Story is a MUST READ… Congratulations on what will soon be a Bestseller!'

I nearly walk off in a daze without checking in my suitcase, causing a momentary security flap. Time for a stiff drink. 

If I am to be an unintended beneficiary of all this week's dramatic reheating of the trans-Atlantic alliance in the wake of the King's historic State Visit, I reflect, then so be it. And I do have the pen to prove it.