Getting to know someone in real depth is, to me, the most unique and enjoyable aspect of being a ghostwriter. Of course, I love the writing: the planning, shaping and conceiving of a book. But it’s getting through to the person behind the book that really fascinates me.

The question had to be asked. ‘What was it like the first time you had sex with John Lennon?’ To her credit, Cynthia, his first wife, only hesitated for a moment to sip her drink, before telling me the story of her first night with John, the two of them making love on a mattress on the floor, in a borrowed room littered with books, art materials and cigarette packets.

‘It was special,’ she said, smiling at the memory. ‘We didn’t care about the mess or the tatty mattress. John told me he’d been lusting after me all term. I was hooked. I would have gone anywhere with him. We lay wrapped in each other’s arms.’ She laughed. ‘Then we suddenly remembered the time. We had to pull on our clothes and race to the station so I could get my last train home.’

To be fair, by the time I asked that question, Cynthia and I had got to know one another pretty well. We’d spent days sipping cool drinks (‘Make mine a martini,’ she would yell to her then husband, Noel) on the veranda of her home in Majorca, as Cyn turned the clock back to the early Sixties. As she talked about the Beatles’ glory days—and the time before the glory days, when she and John were students at art college, and the time after the glory days, when he broke her heart—we’d peeled away the layers and got to the stuff she’d never talked about before.

u meet as strangers and then dive deep and fast into a relationship in which nothing is off the table. People’s most intimate memories, their hopes and fears, regrets, mistakes, secrets and dreams come flooding out. Within days, sometimes hours, of meeting you are asking questions that would sound impossibly intrusive in any other situation. But as the person who is going to write the book with them, you have to do it.

Cynthia’s book, John, was a fabulous glimpse into the life of a man who fired the imagination of people around the world. And there was more. Through Cynthia I met Julia, John’s younger half-sister, who, it turned out, had a wonderful manuscript all about their childhood, tucked into a drawer at home. It only needed a bit of polishing before becoming Imagine This: Growing up with my brother John Lennon, the book that became the basis of the film Nowhere Boy.

Sex reared its head with Julia, too, though this time it was the revelation that John’s self-righteous, forbidding Aunt Mimi—played in the film by Kristin Scott Thomas—had carried on a passionate affair with a man twenty-six years younger than she was, right under the noses of her family.

Mimi, who never had a child of her own, had forcibly removed John from his mother’s care because she disapproved of his mother ‘living in sin’ and having a baby with her new partner, Bobby. Mimi brought in the social workers and took John to live with her, refusing to allow him to go home and insisting that John’s mother was unfit to keep her son, even though John’s father had long since disappeared, making divorce from him impossible.

Mimi hung onto John for the rest of his childhood, leaving his mother broken-hearted and John confused, angry and unhappy. As he told Julia, years later, he never understood why he couldn’t live with his mum, his stepdad and his little sisters.

As it turned out, though no-one knew at the time, Mimi was leading a double life—pious keeper of ‘standards’ by day, saucy minx by night. Mimi, who had turned fifty, was sleeping with her student lodger in the room next to John’s. And she got away with it. No one knew. Julia only learned the story many years later, from the man who had been Mimi’s deepest, darkest secret.

It’s impossible not to be gripped by stories like this—so human, so fallible, so absorbing. There’s nothing as extraordinary as the lives we live. But to reach the deepest corners of those lives, to open up the raw, honest truth, difficult questions have to be asked and answered.

When Julia’s book came out, the reviews were great. My favourite was the one that said, ‘As with Cynthia Lennon’s John, this one has a tone of intimacy and open honesty… I don’t think there will be another Lennon book which will be worth reading after these two.’

That review meant a lot to me, as did Cynthia and Julia’s willingness to tell all. Because intimacy and open honesty are what make a saga like this worth reading. And, for me, only a book that’s worth reading is worth writing.

Caro Handley is the bestselling author of over 70 books