Ian Brady Ian Brady 1/2 Play Slideshow Detectives are hunting for a letter from Moors Murderer Ian Brady that they believe could pinpoint where the body of victim Keith Bennett is buried. Last night it emerged that Brady, 74, has written to one of his long-term visitors finally giving up his 48 year secret of where Keith's grave is located. The letter is thought to be part of documents sent to a member of his legal team. It is believed the individual who received the letter claims it pinpoints the exact location of where Brady and Myra Hindley buried the 12-year-old after snatching and killing him in 1964. Police have not yet seen the contents of the letter. A 49-year-old woman has been arrested as part of the police inquiries. And the MEN can reveal that officers are searching her home in Wales and Brady's cell at Ashworth psychiatric prison in Merseyside. Jackie Powell, who was appointed the murderer's legal advocate under the Mental Health Act in 1999, said yesterday: "I received a letter and a sealed envelope which said on the front 'to be opened in the event of my death'. "He says he doesn't wish to take his secrets to the grave and within the sealed envelope is a letter to Winnie Johnson. "Within that is the means of her possibly being able to rest." Brady and Myra Hindley, murdered five children in the 1960s and buried them in shallow graves on Saddleworth Moor. Both refused to say where Keith's body was buried. Hindley died in 2002, aged 60, but since then Brady has kept his silence over the location of Keith's body. Keith disappeared 48 years ago as he walked to his gran's house in Longsight in the early evening of June 16, 1964. Greater Manchester Police and Keith's mum Winnie Johnson, who is currently in a hospice battling serious illness, have carried out dozens of searches of the moors above Oldham but his body has never been found. Police said last night a woman had been arrested in south Wales on suspicion of preventing the lawful burial of a body. A Greater Manchester Police spokesman said: "On 30 July 2012, Greater Manchester Police received information that led officers to believe that Ian Brady had recently given details of the location of Keith Bennett's body to one of his long-term visitors. "Officers in the cold case unit made inquiries to 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." Brady and Hindley were both convicted in 1966. Chester Assizes was told how Pauline Reade, 16, disappeared on her way to a dance on 12 July 1963 and John Kilbride, 12, was snatched four months later. Lesley Ann Downey, 10, was lured away from a funfair on Boxing Day 1964 while Edward Evans, 17, was killed in October 1965. Brady was jailed for life for the murders of John, Lesley Ann and Edward, while Hindley was jailed for life for killing Lesley Ann and Edward and shielding Brady after John's murder. In 1987, the pair finally admitted killing Keith and Pauline. They were taken to the moors to help police find the remains but they only found Pauline Reade. At a memorial service at Manchester cathedral two years ago Winnie said: "Brady knows where he is. He admitted it and that's how I knew I would never find him alive again. I want the closure, yes, and I want him buried before anything happens to me. But I also want him buried knowing Brady's alive when they do it." 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. "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. "I would ask that we are allowed to examine all the evidence we have recovered and determine whether or not this letter actually exists."