Even if Ian Brady's letter reveals the exact location of Keith Bennett's body, the chances of finding the remains of the 12-year-old on the desolate Manchester moor are slim.
Keith was murdered by Brady and his partner Myra Hindley in June 1964, and despite repeated searches by the police, army and even using a US spy satellite his body has never been found.
Saddleworth Moor where the bodies of three of their other victims were discovered is in the northernmost tip of the Peak District national park, and is a barren stretch of land.
Sparsely populated, the grassy moorland is cut with deep valleys and is largely made from millstone grit, a coarse-grained sandstone.
Although it's believed that the bleak landscape means finding a burial site after almost 50 years is almost an impossibility, the officer leading a search for Keith's body a few years ago believes a new search would not be without hope.
Detective Superintendent Steve Heywood was involved in a renewed investigaiton between 2005 and 2008. Even though the search by Greater Manchester Police proved fruitless, he is still confident that Saddleworth Moor remains as much in place as it did in the 1960s when Brady and Hindley committed the murders, dismissing theories that Brady would not know the location of Keith's body because of the passage of time, or fears that the moorland peat would have shifted over the decades and moved its location.
"If you look back at all the victims they were triangulated so that he could come back," he said.
"Serial killers will generally try to use some sort of landmark - a way of coming back to a particular spot.
"They will revisit their activities on a daily basis. That is what they live for."
He added: "People like Brady know what they are doing. They will have planned everything.
"He will have rehearsed daily what he did. It is my personal opinion that he knows where the body is."
The case was not closed but it could only progress if there was a scientific breakthrough or if Brady revealed where he had buried Keith, he said.
They would not allow the psychotic killer to return to the moors, fearing it could feed his twisted ego, but said he could assist by identifying the location using 3D maps of the area.
"If he (Brady) wants to take the opportunity to do the decent thing then we will listen, but there will be no deals," said Mr Heywood.
"This is his final opportunity to come forward and give the information he knows where Keith Bennett is.
"It has to be something substantial though."
He added investigators would not subject themselves to the "whims" of a "psychopath" in returning to the scene of the murders which he last visited in 1986.
"I am not taking Ian Brady back on the moor," he said. "He will not be released.
"All the experts we have spoken to have advised against doing so."
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