Mr Hancock has detailed the moment he was forced to quit as health secretary after his affair with Gina Coladangelo in the latest extract of his pandemic diaries that is being serialised in the Mail on Sunday.
The shamed Tory MP said Mr Johnson was the “kindest of confidants” during the controversy that saw him break Covid guidelines to engage in an extra-marital affair.
Describing his resignation at Chequers, Mr Hancock writes: “In the end, the great machinery of the State was nowhere. It was just me and the PM, fumbling around with an iPhone.
“He stood on the grass, holding the phone while I said my piece. It took a few goes to get right.
“He nodded sympathetic encouragement so much throughout the first take that the camera waved up and down. In the end it wasn’t perfect, but I was beyond caring: I had to get it out.”
When it became clear the affair was going to be exposed Mr Hancock said the prime minister had assured him he could carry on even though he and Ms Coladangelo had been pictured kissing in his office in breach of his own social-distancing guidelines.
But after the story broke in The Sun last year, he said he found himself “increasingly isolated” politically and was left with no choice but to quit.
“Privately, I was still getting positive messages from colleagues. Publicly, few were willing to defend me. Politically, I was increasingly isolated,” he wrote.
“I went to Chequers to see the PM. I explained that I had been thinking about what had happened and how it had made people feel - and that my mind was made up. The damage to my family and to the Government was too great.
“I told Boris I had to resign.”
Mr Hancock also detailed the moment he received the call from The Sun saying that they knew of his infidelity.
The former health secretary said “knew immediately what I had to do. I needed to tell [my wife] Martha right away, because it needed to come from me and nobody else. I also knew I had to tell the children – it was going to be incredibly painful, but I couldn’t hide away from them forever.”
The publication of his diaries coincides with his return to Westminster from Australia following his spell on ITV’s I’m A Celebrity ... Get Me Out Of Here!