Nearly half a century after she committed her depraved crimes and seven years since she died, images of Myra Hindley continue to exert a unique horror.

Two previously unseen photographs, released yesterday by Greater Manchester Police (GMP) to signal that their decades-long hunt for the body of Moors murder victim Keith Bennett is effectively over, show the blonde-haired killer as a young woman posing with a map and compass against the austere backdrop of Saddleworth Moor.

It was on this high Pennine ground, where Yorkshire meets Manchester, that she and Ian Brady would escape; first to celebrate their destructive bond and later to sexually abuse, murder and bury their victims. Detectives believed the grainy black and white pictures taken around 1964 held the key to finding the body of the youngster snatched from a Longsight street and taken to a remote spot by Hindley where he was strangled by a waiting Brady, becoming the third of the couple's five known victims.

Download the new Independent Premium app Sharing the full story, not just the headlines

Police have remained convinced that soil conditions on the moors meant the 12-year-old's remains would still be preserved somewhere in the peat and water, and called in geologists and aerial photography experts in an attempt to pinpoint the exact location shown in the two pictures.

It was the couple's chilling habit to pose for souvenir photographs beside the last resting places of the children they killed. But yesterday, in a surprise announcement, police revealed the existence of a hitherto secret operation known as Maida that had been ongoing since 2003.

Hopes of success had been high after traces of chemicals associated with dead bodies were discovered in the lonely pools around Shiny Brook. But these were dashed when they were found to be naturally occurring.

Despite the vast efforts of officers, an array of scientists, psychologists and forensic archaeologists the search was ultimately thwarted by the defiant silence of 71-year-old Brady, who is living out his days in Ashworth high security hospital in Merseyside. In the end all that was unearthed during the operation was a decomposed set of sheep bones.

Detective Chief Superintendent Steve Heywood, head of GMP's serious crime division, described yesterday how he walked to work each day in the shadow of the moor. He said he was continually reminded of Keith's disappearance and the police's failure to recover his body to allow his 75-year-old mother Winnie Johnson to bury her son. Officers will now no longer search the high wilderness barring a genuine and substantial confession from Brady or major scientific breakthrough. He said the killer would not be allowed to return to the moor and that police would not respond to the "whims" of a "psychopath". Brady and Hindley, who died in prison aged 60 in 2002, were convicted in 1966 of murdering Lesley Ann Downey, 10, John Kilbride, 12, and Edward Evans, 17. In 1986 both were taken back to the hills to help in the quest for two undiscovered bodies following Brady's confession to killing Keith Bennett and 16-year-old Pauline Reade, who was found in 1987.

Brady has refused to co-operate with the latest inquiry, waving investigators away from his hospital bed when they tried to question him. Should he finally reveal his secrets, said Mr Heywood, he would be asked to identify the spot with the use of a 3D virtual representation. "If he [Brady] wants to take the opportunity to do the decent thing then we will listen, but there will be no deals. This is his final opportunity to come forward and give the information. He knows where Keith Bennett is," he said.

Police have taken specialist advice not to allow Brady to revisit the scene of his crimes for fear of fuelling his personal gratification and believe the cost of protecting him during such a visit would be too much. They insisted that the case remained open even though the search of the moors had entered a "dormant phase".

For Keith Bennett's mother, yesterday was another day in a life which has been destroyed by the disappearance of her son. She again publicly begged Brady to own up before it was too late and allow her to remember Keith's short life with a service at Manchester Cathedral. "I'm pleading with him to get to me or the press or the police and tell me where Keith is. It is the last time it will be done," she said. Breaking down as she caught a glimpse of the moor on television images of the search shown during a specially convened press conference, she said: "It is not fair on me, what I have had to go through. I did not ask him to be picked-up and murdered.

"It's a nightmare; it's been a nightmare for the last 45 years how I have carried on – 45 years in limbo. If he's got any decency or respect for anybody it should be me," she said. Ms Johnson's lawyer David Kirwan, who has met Brady twice in an attempt to persuade him to talk, re-iterated his client's plea.

"Today I am calling on Ian Brady to declare that he will do what he says he can do. I am ready to meet with him again to help bring to an end the appalling ordeal Keith's mother has endured all these years."