A TV documentary about Moors murderer Ian Brady will air tonight with the approval of Winnie Johnson's family, broadcaster Channel 4 confirmed.
Mrs Johnson, 78, whose son Keith Bennett was killed by Brady and Myra Hindley in 1964, died on Saturday without ever finding out where the 12-year-old was buried.
Her death came just hours after it emerged that police are investigating whether a letter exists in which Brady, 74, apparently discloses the location of Keith's body.
Brady's mental health advocate, Jackie Powell, told the documentary that Brady gave her a sealed envelope containing a letter to pass to Mrs Johnson in the event of his death.
That information was passed to police and Ms Powell, 49, was arrested on Thursday at her home in Llangennech, South Wales, on suspicion of preventing the burial of a body without lawful exercise.
In a statement, Channel 4 said: "This documentary will be airing tonight as planned following consultation with Winnie Johnson's family and with their approval.
"There will be tweaks to reflect Winnie's sad passing but otherwise the film will remain unchanged."
The closest Mrs Johnson came to giving Keith a funeral was to hold a memorial service at Manchester Cathedral two years ago in which she tearfully told the congregation: "I'm Keith's mother... he's there on the Moors, I want him back."
Keith's brother, Alan Bennett, said yesterday that the death of their mother must not be seen as closure to the case and vowed to continue the fight to locate the remains of the 12-year-old.
Writing on his website, www.searchingforkeith.com, Mr Bennett, who was nine when his brother was taken, said: "As far as I am concerned, until Keith is found then he is still in the possession of Brady and Hindley."
Detectives are examining a large number of seized documents but have so far found no letter or any evidence to suggest Brady has disclosed the location of Keith's body.
Ms Powell, who is also an executor of Brady's will, remains on bail pending further inquiries.
It is understood she claims she returned the sealed envelope to Brady before her arrest.
A search of Brady's quarters at Ashworth Hospital in Merseyside, where he has been detained since 1985, has also failed to uncover the alleged letter.
Their victims were sexually tortured before being buried on Saddleworth Moor above Manchester.
Pauline Reade, 16, disappeared on July 12 1963, and John Kilbride, 12, was snatched in November the same year.
Keith Bennett was taken on June 16 1964, after he left home to visit his grandmother. Lesley Ann Downey, 10, was lured away from a funfair on Boxing Day 1964, and Edward Evans, 17, was killed in October 1965.
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.
Keith's body was the only one never to be found.
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