Ian Brady gave details of the location of Keith Bennett's body to one of his long-term visitors, police say

Moors murderer Ian Brady has finally revealed the location of the body of 12-year-old Keith Bennett, police believe.

Greater Manchester police said in a statement on Thursday night that Brady had revealed the whereabouts of his fourth victim to one of his long-term visitors in a letter, and officers had carried out arrests in relation to the information.

A 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 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 today.

"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."

The 12-year-old disappeared on 16 June 1964 while on his way to his grandmother's house in Longsight, Manchester, and although he is known to have become a victim of serial killer Brady and accomplice Myra Hindley, his body was never recovered. Police believed he was buried somewhere on Saddleworth Moor, above Manchester, where Brady had taken other victims.

The two were responsible for the murders of five children in the 1960s, after driving them on to the moor. While Hindley said she stayed in the car, Brady sexually tortured and killed his victims on the moor.

The victims include 16-year-old Pauline Reade and John Kilbride, 12, who disappeared in July and November 1963; Lesley Ann Downey, 10, who was lured from a funfair on Boxing Day 1964 and Edward Evans, 17, killed in October 1965.

Brady was given a life sentence in 1966 for the murders of Kilbride, Downey and Evans, while Hindley was jailed for life for the murders of Downey and Evans, and for shielding Brady. The two admitted to killing Bennett and Reade only in 1987.

Hindley became religious in later years and made attempts to be released, but died in jail in 2002 aged 60. Brady was declared criminally insane in 1985 and has been held at the high-security Ashworth hospital on Merseyside. He has mounted hunger strikes and said he wants to die.

Keith Bennett's family, especially his mother, Winnie Johnson, have long agonised over his whereabouts, Brady refusing to say where on Saddleworth Moor the body could be found.

Johnson made a number of pleas to Hindley to help discover where her son was buried. Johnson said in December she wanted Brady to tell her face-to-face of the whereabouts of her son. The 78-year-old has recently been diagnosed with cancer.