Police investigating an unrelated minor crime came to his tiny apartment in Hafnarfjordur. They arrested Saevar and his girlfriend, Erla Bolladottir, taking them both away from their 11-week-old daughter.

In December 1975, nearly two years after the first disappearance, Saevar's luck ran out.

The police certainly knew the slight young man. He was a small time crook, who had been caught importing cannabis from Denmark. He had, until now, kept out of prison.

It wasn’t just his Polish name that made Saevar stand out. His long dark hair and almost girlish good looks set him apart from the pale Icelanders.

In custody, Erla owned up to the crime. She was about to leave the interrogation room when the police suddenly produced a photo of a handsome boy with long hair.

She recognised him at once from a school disco several years earlier.

“I remembered him as he liked me that evening. He was good looking. We had a pleasant chat and I was flattered.”

The boy in the photograph was Gudmundur Einarsson.

It has never been clear why, so long after Gudmundur’s disappearance, the police began asking Erla about it. She remembered the night he had gone missing though.

It wasn’t just the bitter cold, the snow or the party she had been dragged to and couldn’t wait to leave. That had been the evening she had had the nightmare - in which she heard Saevar and his friends whispering outside her window.

When she told her interrogators about this, they latched on to it.

Maybe, they thought, it hadn’t been a dream. Perhaps she had witnessed something traumatic, the aftermath of a murder.

She remembers the head of the investigation becoming very intense, getting right up into her face: “We are going to help you recall everything. You will not be able to leave here until you tell us what happened to Gudmundur Einarsson.”

It was no idle threat.

Erla was warned that for serious crimes there was no limit to the time she could be held in solitary confinement.

Alone in her cell that night, Erla couldn’t sleep. She kept trying to work out what was real and what was her imagination.

One thought kept returning to her: “Is it possible they killed someone in the apartment and I saw the whole thing and I can’t remember?”

During the following days, there were long interviews, without a lawyer being present. Her interrogators were generally pleasant and helpful, saying they wanted to unlock her memories. She was “just desperate to get out of there and get back to my baby,” she says.

After one interview, which went on for more than 10 hours, the police prepared a statement which Erla signed, saying she had seen Saevar and three of his friends with a body wrapped in a bed sheet - the body of Gudmundur Einarsson.

Erla was convinced, wrongly it turned out, that the statement would be dismissed as nonsense.

When he was presented with it, Saevar suddenly admitted he might, after all, know something about the death of Gudmundur.

He started talking, admitting his part and going on to implicate his closest friends.