It was not until 20 years later that they confessed to killing Keith Bennett and 16-year-old Pauline Reade.

Mr Staff, who has written a book called The Lost Boy, said detectives handed the photos to Hindley’s mother after the trial. “The police had no choice but to return them,” he said. 

“When Brady found out, he wrote to Hindley many times demanding the photographs.

“Hindley eventually gave them to him when Brady wrote that he would send somebody to her mum’s home to get them.” 

In 1987 Brady was allowed out to help police search for the burial site on Saddleworth Moor, near Manchester.

But he either would not or could not identify the spot. “Afterwards Detective Superintendent Peter Topping visited him and Brady showed him the photos,” said Mr Staff. 

“When Topping asked him why, Brady said he was just illustrating how much the topography of the moors had changed over the years.

“I believe Brady may well have been showing him photos of Keith’s grave and taking pleasure in the knowledge that he knew something the police didn’t. Brady was a good photographer and he was meticulous about keeping records.

“It was all about control. Essentially he was recording what he thought was the perfect crime. At least one of the photos is believed to show children standing on the moors. He took them there and posed them next to what I believe was Keith’s grave.”

Last night Mrs Johnson, of Longsight, Manchester, said: “Brady has been playing cat and mouse with us all these years.”