Imagine an America where the volatile president gets so inflamed by a war of words with North Korea, that in a fit of pique he finds himself just seconds away from hitting the nuclear button.

That terrifying – and not entirely improbable – scenario sets the gut-wrenching pace for Sam Bourne’s latest thriller, To Kill The President, which fittingly hits the shelves on 4 July.

At the heart of the edge-of-the-seat drama is Maggie Costello, a seasoned Washington operator, who unwittingly stumbles across a murderous plot against the president, but the weight of her moral dilemma is immense.

Should she save the president’s life – but leave the free world at the mercy of a crazed demagogue – or commit the ultimate act of treason against her Commander-in-Chief and risk plunging the country into civil war?

One could argue that the plot sails dangerously close to the winds of current world politics, but any similarities to real life are “solely down to the reader’s imagination”, chuckles journalist Jonathan Freedland, who has been penning thrillers under his Sam Bourne pseudonym (a blend of his younger son’s name and the popular spy series starring Matt Damon) since 2006.

Freedland, who served for four years as the Guardian’s correspondent in Washington, keeps tight-lipped over whether he was inspired by the current president – “I can’t at all control what readers have in their mind” – but admits the first kernel of an idea came to him while covering the 2016 US election campaign.

“Two of the most important words for a thriller writer are: ‘What if?’”, explains the 50-year-old author, who came across an intriguing story concerning American novelist Philip Roth.

“In a book Roth was reading about the Republican Party in 1940, he read that they didn’t have a presidential nominee and there was talk of drafting in Charles Lindbergh, celebrity aviator and a staunch anti-Semite.

“In the margins of the book, Roth wrote, “What if they had?” and from that came his brilliant novel, The Plot Against America, in which he imagines a Nazi sympathiser who becomes the president.

“Similarly, during the course of the Trump-Clinton campaign, I began to think, what if you were a patriot and loyal to your party, but then you came to the conclusion that the leader of your party was actually a danger to America and the world? Where would your duty lie in that situation?”

As he mulled over the idea, the married father-of-two began to research the “trappings of the president”, from the pomp and ceremony of his motorcade, to the public’s obsession with the First Lady and life behind doors at the White House.

But material gains aside, Freedland discovered just how powerful the President actually is.

Sam Bourne cover

“He’s actually known as ‘the nuclear monarch’”, gasps Freedland. “In many ways, the president is quite constrained under the American system and even executive orders have to go through the courts. But one of the least restrained powers – and it was deliberately designed this way by Harry Truman – is the nuclear power, where it just goes through nobody.

“People assume if this president wanted to order a nuclear strike, he would have to consult with others.

“But there is no chain of command, there is no process. He just presses the button. I thought that was inherently frightening and dramatic.”

Stories about the nuclear threat, political assassinations, espionage and conspiracy theories have fired the imagination of Freedland ever since he was a youngster.

Day of the Jackal, The Parallax View, Three Days of the Condor, The Odessa File – I just lapped them all up.”

While he admits to being an avid reader, by day he is more well-known for his career as a journalist. I ask if he prefers the realms of fiction to the pursuit of accuracy and truth.

“Actually, I used to joke that fiction is harder than journalism, because in fiction you can’t make things up,” he quips. “It’s really interesting just how exacting the readers are about accuracy.

“For example, you could be reading Dan Brown’s latest thriller, which will take you on wild flights of fantasy about Jesus, but if you have a character who gets on the Northern Line at Green Park station, the reader will hurl the book across the room and say, ‘I can’t believe a word of this, its complete rubbish!’

“They expect the real world things to be properly researched and accurate.”

“I used to joke that fiction is harder than journalism, because in fiction you can’t make things up”

From poring over government documents detailing nuclear codes and assassination plots to travelling around the world, Freedland draws upon real-life situations and experiences in his writing. That also includes his Jewish heritage.

His first three Sam Bourne books – The Righteous Men, The Last Testament and The Final Reckoning – all revolve around Jewish themes.

Even in this latest outing, Maggie Costello is first prompted to the existence of an assassination plot following the death of the president’s Jewish doctor.

Speaking of Maggie, she is perhaps the one departure from reality that Freedland credits with making his stories all the more believable.

“One of the least strong aspects of my first novel, The Righteous Men, was the central male character, a British-born reporter, who was a bit too similar to me.

“A fast-track way to cure that was to create a woman, because inherently she couldn’t be like me – and readers really responded to her.

“It required an imaginative leap, but that can only be a good thing for a writer to do.”

To Kill The President by Sam Bourne, published by HarperCollins, priced £7.99 (paperback) is out on 4 July