The mental health advocate of the Moors murderer Ian Brady has been arrested on suspicion of preventing the burial of Keith Bennett, one of Brady and Myra Hindley's five young victims.
Bennett was 12 and on his way to visit his grandmother when he was taken and murdered by the pair on 16 June 1964.
Like the other youngsters snatched by Brady and Hindley – Pauline Reade, John Kilbride, Lesley Ann Downey and Edward Evans – he was killed and buried on Saddleworth moor above Manchester.
Neither Brady nor Hindley, who died aged 60 in 2002, has revealed where Bennett's body was buried, despite repeated pleas from his mother, Winnie Johnson.
Police confirmed on Friday that Jackie Powell, who was appointed as Brady's advocate under the Mental Health Act in 1999, had been arrested in south Wales on suspicion of preventing the lawful and decent burial of a body without lawful excuse.
Powell was apparently detained after telling a Channel 4 documentary that Brady gave her a sealed envelope to pass on to Johnson in the event of Brady's death.
In a statement, Greater Manchester police said they had recently received information that led them to believe Brady had finally disclosed details of the location of the body to one of his "long-term visitors" at Ashworth high-security hospital where he is being detained.
The force did not name the suspect but said a 49-year-old woman had been arrested in south Wales and remained in custody for questioning.
A police spokesman added: "Officers in the cold case unit made inquiries to verify the accuracy of this report and have since had extensive contact with Ashworth hospital and Keith's close family. As a result, warrants obtained under the Police and Criminal Evidence Act were executed at Ashworth hospital and a private address in south Wales.
"A 49-year-old woman has been arrested in south Wales on suspicion of preventing the burial of a body without lawful exercise and remains in police custody for questioning. Searches of both locations are ongoing."
Martin Bottomley, head of investigative review of Greater Manchester police's major and cold case crime unit, said: "The Moors murders cast a long and dark shadow over the history of our region but in 2009 we reluctantly concluded there was no longer any specific information to identify new search areas and the investigation to find Keith entered a dormant stage. However, we have always stressed this is a case we will never close.
"We have been, and always will be, open to pursuing any new lines of inquiry that arise from significant scientific advances or credible and actionable information."
He added: "I want to be explicitly clear about this: Ian Brady has not revealed to police the location of Keith's body. What we are looking at is the possibility – and at this stage it is only a possibility – that he has written a letter to Keith's mum, Winnie Johnson, which was not to be opened until after his death. We do not know if this is true or simply a ruse but we clearly have a duty to investigate such information on behalf of Keith's family.
"Since Keith was so cruelly taken away all those years ago, our thoughts have always been with his family as they try to come to terms with what happened. All they want is to finally be able to lay Keith to rest. What I would ask is that the media respect their privacy at this time. Winnie herself is very ill and continued speculation about this letter will only cause the family more upset."
The force later said the woman had been bailed for three months.
The Guardian understands that officers seized documents from Powell's house, but believe there is no clear evidence that Brady has revealed the location of Keith's grave.
It is thought that Johnson is not yet aware of the recent developments. Her lawyer, John Ainley, told the Press Association: "Winnie has always believed that Ian Brady knew where her son was buried. She never thought anything else. He had a dialogue with Winnie some years ago and she was certain that he could have provided information that would have given her closure in this harrowing case."
Last December, Johnson said she wanted to hear face-to-face from Brady where her son was buried. She renewed her plea last month, saying in a letter to the 74-year-old killer that her dying wish was to know where Keith's body was.
The makers of the documentary said they had not seen the envelope.
The documentaries commissioning editor and editor for Cutting Edge, Emma Cooper, said: "No one can verify the contents of the envelope and therefore what information it does or does not contain but given the enormity of the implications as suggested by Brady's letter, we felt we had a responsibility to inform the family via their family liaison officer.
"Winnie's poor health was foremost in our decision-making and this is why we have decided to bring forward the broadcast of the film and make the existence of the envelope public."
The film, Ian Brady: Endgames of a Psychopath, will be broadcast on Monday at 9pm. In an interview she gave for the programme, Powell said she had received a letter of instruction and a sealed envelope from Brady via his solicitors. She explained that the letter of instruction stated the additional envelope contained three letters – one apparently addressed to Johnson.
Powell, who has professional obligations in her capacity as executor and her role as Brady's mental health advocate, told the documentary she had not opened the sealed envelope so could not be certain of its contents. But she told the Daily Mirror Brady did not want "to take his secrets to the grave", adding that the document could afford Johnson "the means of her possibly being able to rest".
Brady was jailed for life at Chester Assizes in 1966 for the murders of John, Lesley Ann and Edward. Hindley was convicted of killing Lesley Ann and Edward and shielding Brady after John's murder, and jailed for life. In 1987 the pair finally admitted killing Keith and Pauline.
Both were taken to Saddleworth moor in 1987 to help police find the remains of the missing victims but only Pauline's body was found.
Brady was due to go before a mental health tribunal in July, but it was delayed after he suffered a seizure. The tribunal was to consider his application to be transferred to a Scottish prison and be allowed to die. He has been tube-fed since refusing food 12 years ago.
David Wilson, a professor of criminology at Birmingham City University and an expert on serial killers, expressed doubt about the existence of the letter.
"There is no new information here," he said. "Ian Brady went back to the moors in 1987 and said to the police officer: 'Who moves that mountain?' They stopped the investigation then because it's quite clear he didn't have a clue where the body was. This is not about Keith Bennett, or Winnie Johnson, it's about Ian Brady.
"He is a master of trying to inject what is broadcast and printed about him, and making sure we interpret the story in the way he would like us to interpret it. He's unique in the sense that most serial killers don't want to talk and communicate. Ian Brady communicates all the time. When you assess what he writes it is usually self-serving nonsense, not remotely reliable."
Wilson said he was on the moors four weeks ago and saw the tributes Johnson had left for son.
"I want there to be a positive ending, but I wouldn't trust him as far as I could throw him. He's legally insane, so why do we believe he's going to say anything at all that can be reliable?"
Documentary-maker Paddy Wivell told Radio 4's Today programme: "I think we probably have to approach it with some sense of caution too. This seems to me like very much part of Brady's pathology, one of power and control.
"He is a sadistic psychopath and it would appear that this is some sort of victory dance, a kind of power game, in the fact that he constantly puts conditions on things. The condition that it can only be opened in the event of his death is consistent with this kind of behaviour over the years."
Lord Pendry, who was the MP for Stalybridge and Hyde for 31 years, told the Guardian he was responsible for persuading Brady to visit the moors in 1987 and to "match his words with deeds".
"I got Brady up to the moors as my constituency was in Hattersley and he was a constituent. It's just now that people are talking as if he's never been up there," Pendry said.
He wrote to Brady in September 1987 and then visited him in hospital. "I spent five hours with him – longer than anybody else," he said. "I convinced him to go up and look for the boy Bennett's body. Then I went to Manchester police and they took him up there. He couldn't find it.
"It was an almost impossible situation. Myra Hindley took them to Lesley Ann Downey's grave. He was anxious to upstage her."
Pendry said: "I don't know what's new about the situation. He has been up there previously and couldn't find it then."
He questioned whether Brady was "leading more people up the garden path".
