Winnie Johnson has died without the knowledge she so desperately longed for - the location of her son's body.
Keith Bennett was murdered by Ian Brady and Myra Hindley in 1964. He was the only victim of the Moors Murders whose body was never found.
ITV News' correspondent Sally Biddulph reports:
More top news
Five people were killed and dozens more were injured after a car and knife attack in the capital on Wednesday afternoon.
Among those expected to attend the ceremony will be former US President Bill Clinton and ex-Northern Ireland first minister Peter Robinson.
Five people have been killed and 40 injured after a car and knife attack in London on Wednesday.