In the early hours of Friday, September 18th, 1970, while staying with a girlfriend in London, Jimi took some sleeping pills. Nobody knows for sure how many pills he swallowed, or whether he understood what he was taking. The drug was Vesparax, a strong barbiturate. Half a tablet was enough to put a man to sleep for eight hours – Jimi may have swallowed as many as nine. He had also been drinking. This was foolish and reckless but it was in character.

During his years on the road Jimi had got into the habit of using drugs indiscriminately. "Jimi would take a handful of shit, not even knowing what it was," his friend Deering Howe has said.

It is certainly easy to imagine Janis feeling lonely as she returned to her hotel room in Hollywood after her last recording session. As she sang in "A Woman Left Lonely," one of the last songs she sang, she knew that her boyfriend was taking her for granted. At around one a.m. on October 4th, 1970, she got her heroin kit out and injected a vein in her left arm. Then she went to the cigarette machine in the hotel lobby, returning to her room with a pack. She closed the door, started to undress and reached to put her packet on the nightstand. As she did so she keeled over, hitting her face on the table as she fell to the floor, where she was found dead the next day.

The cult of Jim Morrison grew posthumously, taking off in 1979 when Francis Ford Coppola used "The End" in the soundtrack for Apocalypse Now. Part of the cult of Jim was the coincidence of him dying at the same age as Brian, Jimi and Janis.

The 27 link helped reinforce the idea that Jim had been special; that his death was fated; that there was something weird going on. The fact that Jim's girlfriend had died at the same age underlined the weirdness of the coincidence.

This legend was familiar to everybody with an interest in popular music by 1994 when Kurt Cobain decided to join the club.

Jones' death at his country home in England in 1969 seems to be the result of his foolish behavior. To mix alcohol and drugs and then dive into the swimming pool was to swim directly into the arms of death.

As clear as this seems, the death of Brian Jones has become one of the most persistent mysteries of rock & roll, with many people questioning the official version of what happened. Even members of the Rolling Stones have expressed doubts.

"And still the mystery of his death hasn't been solved," Keith Richards has said. "I don't know what happened, but there was some nasty business going on.”

Kurt Cobain's body was discovered by an electrician on Friday, April 8th, 1994. The answer to the question posed by the authors of Who Killed Kurt Cobain? is simple: Kurt Cobain killed himself. He did so with sudden, self-inflicted violence, leaving written evidence of his state of mind.

Kurt's substance abuse counselor remembered how worried the musician had been about losing his home in a lawsuit: "Suicidal people tend to want to make a statement," Nial Stimson said. "I just kind of felt he killed himself in his house [as if to say], "You're not going to take my house, no matter what..."

What Amy's state of mind was when she took her last gulps of vodka at home in London in July 2011 is impossible to know. She had said there were things she still wanted to do with her life, but she seemed unable to take action. Despite being a remarkably honest and open person in many respects, she had always been cagey about her inner life.

Observing Amy as we have, there is a strong sense that she was sick of her career. Like Jimi Hendrix and Kurt Cobain, she had become a prisoner of her image. And, as with Janis Joplin, her man was glaringly absent at the end. So were other people Amy had depended upon and, in many cases, exhausted.