Insofar as they could be trusted, the hints in Jack’s letter went beyond forgery and suggested … Well, what?

Back at my desk, I shelved all my other obligations and belatedly undertook my due diligence on Hunter.

Bit by bit, I pieced together an outline of his life from clues on the internet.

His Wikipedia entry said he’d been born in 1948 in Santa Barbara, the only child of Vincent and Betty Gould. That made him about ten years older than I’d imagined. Betty had been a kindergarten teacher. Vincent, who worked for General Electric, had died suddenly when Hunter was seven.

There was no mention of an interest in books. If there was a key to Hunter, it seemed more likely to be music. In a scratchy interview from the early 1990s that someone had posted on YouTube (‘Adding comments has been disabled for this video’) Hunter told a Dutch television audience that his earliest memories were of his mother playing German waltzes on an old accordion.

Elsewhere, Hunter himself made the connection between his early bereavement and his immense appetite for work. He boasted to one interviewer that he worked every day of his life, except his birthday, which he spent pedalling his age in miles on a stationary bicycle. He put this drivenness down to his early experience of death. ‘I realised early on that time is the greatest blessing there is,’ he said.

He’d spent a couple of semesters at an expensive liberal arts college, but decided he couldn’t bear the thought of delaying his encounter with real life for four years. He and a friend called Douglas Martens dropped out and went into business together.

‘Dougie and I were joined at the hip,’ he told a journalist from a music magazine. ‘We bonded over the fact that we both lost fathers young. His died in Korea. I remember as freshmen we made a list of everything we wanted to do together, and I mean everything – we filled a yellow legal pad: start companies, explore the world, visit other galaxies. Then we got depressed because we realised that we wouldn’t live long enough. I remember Dougie jokingly crossed out everything on the list and wrote: “Cure ageing.” We both decided to drop out then.’

So his claim that he’d been to law school turned out to be a lie; he hadn’t even finished university. But I learned from other sources that the falsehood was a typical Hunter manoeuvre: bold, self-aggrandising and oddly unnecessary. Several friends and former colleagues spoke warmly about his charisma and his empowering belief in himself. But its flipside was an impatience with the mere facts. ‘Sometimes, when you’re around Hunter, he can make reality seem a little bendy,’ said one ex-employee, who had found himself walking away from a well-paid job to come and work on Hunter’s startup for free.

Hunter and Douglas both took drugs and both were in and out of rehab. But Douglas died in a motorcycle accident in 1978 before ever quite managing his own tricky transition from the drug years to the stationary bicycle years.

‘I think about Dougie all the time,’ Hunter said. ‘If I ever feel like playing hookey, I think about him and it’s what gives me focus and it’s the reason for my longevity in this business.’

By the late 1980s, growing increasingly exasperated with the behaviour of recording artists and with his fortune, in any case, already sizable, Hunter had begun to collaborate with Silicon Valley types to create computer programs that could compose music without any human intervention. Hunter was typically bullish about the potential of these ideas. ‘In less than a hundred years,’ he was quoted as saying, ‘the majority of the music we listen to will be composed by what we now think of as computers.’

It was hard to know what to make of it. Did he really believe this? Or was it one of those loopy enthusiasms that his mania or disinhibition compelled him to share with the interviewer?

Reading about his life, I understood that he was a product of a particular place and moment in American history. The California Hunter had grown up in was the Ironbridge of a second Industrial Revolution. Among his friends and acquaintances were the people who altered the technological circumstances of the twenty-first century. By the time they were in their sixties, they had lived long, contradictory lives. One minute they had been dropping acid and protesting against the Vietnam war. The next, they put on ties and were bidding to design the software for missile guidance systems. Hunter embodied these paradoxes. He had been a barefoot dropout, now he was a notoriously demanding boss. He had embarked noisily on various methods of personal growth, from Zen to EST, but still seemed uncomplicatedly entitled: a pampered mummy’s boy who had never had reason to doubt his own importance.

Hunter had been quick to see the business potential of economic liberalisation in the Soviet Union. At one stage, in the early 1990s, he’d been part owner of a Moscow radio station and an investor in a number of joint enterprises. It was hard not to be impressed by his energy and the breadth of his interests. It was hard too not to wonder if this drivenness was part of his mental instability. Surely there was another Hunter – the enantiodromic partner of the visible one – who stayed in bed for weeks at a time, complaining he was hollow?

And I kept thinking of the question he’d asked at our second meeting, when he had stared across the table at me with that strange, zealous look in his eyes and asked: ‘Have you known much death, Nicholas?’

*

I rang Hunter early on the Monday morning. He sounded surprised to hear from me, but he agreed to see me that afternoon.

The building which houses the UK headquarters of Hunter’s various businesses is a converted candle factory beside the Regent’s Canal. The side you approach is all yellow stock brick and cast-iron pulleys, but the rear of the building with the canal view has been transformed into a bizarre eruption of asymmetric green glass which partly resembles a collapsing Mayan pyramid.

Inside, there was an air of understated magnificence: behind a long white desk sat an improbably glamorous receptionist with false eyelashes so big and silver that they opened and shut like Venus fly traps. There was a goldfish pond entombed beneath glass bricks by her feet, a Giacometti by the entrance and, most uncannily of all, a naked man lying at full stretch on the heated slate floor of the reception area.

Hunter came to fetch me himself. He was deeply tanned, but he’d lost so much weight that the effect was to make him look sun-dried, like a raisin, and vaguely reptilian. ‘Dead dad,’ he said, enunciating the words slowly, as he smiled and offered me his hand.

Reading about Hunter, I had learned of his talent for identifying someone’s vulnerabilities. A former colleague had told Rolling Stone that Hunter’s management style was an acutely toxic combination of emotional intelligence and a taste for personal humiliation. But what he had just said was so extraordinarily cruel that I was staggered. The words were barely out of his mouth before I’d seen all the deep and unpleasant layers of significance he had invested in them.

At one level, he was saying that he knew all about me, about the formative experience of my father’s death. I knew that, but to have him know it was demeaning. And he was going further, making a link between that loss and my feelings about Jack; feelings which he was implying were inappropriately strong. I felt like he’d stabbed me. He must have seen the change in my expression.

‘Ron Mueck,’ he said, pointing at the naked man. ‘The sculpture is called Dead Dad. We commissioned a life-size copy from the artist.’

‘Of course,’ I said, shakily.

‘It’s always good to see you,’ he said, as we got into the lift. ‘And I have to say that Sinan and I are both touched by your concern about Jack. He’s in safe hands, he’s doing very well. There’s no need for you to worry.’