Police have arrested Jackie Powell, the mental health advocate of Moors Murderer Ian Brady. But who is she, and how is she connected to Mr Brady?
Detectives are investigating whether Ian Brady may have revealed information about where one of his victims, 12-year-old Keith Bennett, is buried.
Brady may have passed details of the location to his mental health advocate, Jackie Powell, during a visit to his psychiatric hospital.
Ms Powell was arrested in south Wales on suspicion of preventing the lawful burial of a body.
Jackie Powell was appointed Brady's legal advocate under the Mental Health Act of 2009.
The legislation states that anyone detained under the Act is entitled to the support of an independent mental health advocate (IMHA) to provide information about their rights under the act and any aspect of their care or treatment.
The advocate represents the patient at formal meetings with medical and police authorities, and also advises the patient on their right to have a second opinion from an independently appointed doctor.
Jackie Powell has fulfilled this role for Ian Brady.
Police launched their investigation after Ms Powell told a Channel 4 documentary that Ian Brady gave her a sealed envelope to pass to Winnie Johnson, the mother of his 12-year-old victim Keith Bennett, in the event of his death.
Ms Powell said: "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."
Detectives examining documents seized from Ms Powell's home have so far found no evidence to suggest Brady has disclosed the location of Keith's body. Ms Powell has since been released on bail pending further inquiries.
Paddy Wivell, who made the documentary, has questioned Brady's motives behind handing over the letter to Ms Powell.
He told BBC 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."
The role of the legal health advocate is different to that of the "appropriate adult" depicted in the recent ITV drama of the same name, which examined the relationship between serial killer Fred West and Janet Leach.
Ms Leach was a social worker-in-training who, in 1994, was asked by police to sit in on interviews with Fred West.