Tormented to the last after a lifetime of campaigning, the 78-year-old died without fulfilling her cherished wish to find her son's makeshift grave on Saddleworth Moor and give him a Christian burial.
Ian Brady and Myra Hindley murdered the 12-year-old in 1964, the only one of the five young victims whose body has never been found.
At the service at St Chrysostom's Church, in Victoria Park, Manchester, where Mrs Johnson, a widow, was a regular parishioner and Keith attended Sunday School, the names of her son's killers were never uttered.
Instead her family, friends and members of the public among the mourners heard tributes to a courageous mother who battled on despite a life touched by tragedy.
A former cleaner and worker in hospital kitchens, her desire to know became ever more desperate after she was diagnosed with the cancer that took her life on August 18.
Canon Ian Gomersall, rector of St Chrysostom's, told mourners: "I will not go into the detail of this, nor will I name here the perpetrators of that evil. What I will do is pay tribute to this remarkable woman. I know my words of tribute will be shared by so many people.
"I pay tribute to Winnie's courage and determination to bring her son back to her family.
"I pay tribute to Winnie and her family's resolve to give Keith a final resting place, which has been an inspiration to so many over the years, and we thank God for this encouraging example."
Canon Gomersall said Mrs Johnson had shown "that we, everyday people, can have courage, strength, hope and determination, whatever assails us".
And while she was a woman of sorrow, she was also someone who "even in the midst of her grief", could find hope and joy, and showed that love, faith, hope and courage would prevail over darkness.
Mrs Johnson was a humble woman of modest background, made to live in the public eye.
The search for Keith took a working-class woman with a sense of humour to the corridors of power, dealing with a number of home secretaries.
While Brady and Hindley took her son, they could not take her dignity or her pride, which never failed and she was a symbol of courage and decency.