On February 12, 1993, 10-year-olds Robert Thompson and Jon Venables snatched two-year-old James Bulger from a Merseyside shopping centre, caused him horrific injuries and then dumped his body on a railway line.
The murder gripped the nation, and questions are still left to be answered today.
Phil Roberts was one of the lead detectives on the case who arrested, interviewed and charged Robert Thompson with the murder.
He grew up in Llanrhaeadr, left to work for the serious crime unit at Merseyside Police, before returning to his Mid Wales roots to enjoy his retirement.
But the Bulger case is never too far away from his mind, with the media attention it is still given today.
He said: “You have to learn to sort of shut it to the back of the mind, but with the media coverage, the anniversaries, it will never really go away.
“These kids were 10 years old, sitting in that room it was hard to grasp that the boys could have caused these injuries. You just don’t think a 10-year-old can do that.”
The pair beat James to death before dumping his body.
They went on trial, and were also charged with the attempted abduction of another small boy on the same day.
“There is no doubt they knew what they were doing that day, they set out to kill someone, to kill a little boy,” added Mr Roberts.
“The injuries they caused to James were horrific, and they tried to make it look like an accident by putting his body on a railway track, that is why they knew what they were doing.”
A Channel Four documentary aired last week has come under criticism from James Bulger’s mother, and the general public.
The programme centres around discussions of how the trial was handled, if the boys were old enough to do what they were doing, and if they should have ever gone to trial at all.
Lawyers acting for the killers suggested that it should not have gone to trial, and that the age of criminality in the UK, which currently stands at 10, should be increased.
The Llanrhaeadr detective disagrees, and believes a flaw in the whole ordeal was that Thompson and Venables never served time in an adult prison.
After being sentenced to eight years, their tariff was increased to 15 years after a petition was sent to the then home secretary Michael Howard.
However a high court judge reduced the sentence, and pair were made eligible for release in 2001 after a parole board believed they were no longer a danger to the public.
They were released with new identities, new backgrounds, and new passports.
Mr Roberts added: “I think the age of criminality is correct, it doesn’t need to go up. Children would manipulate it and take advantage of it.
“They were evil little children, and one thing I think should have happened that didn’t, is that they should have served time in adult prison.
"They were still juveniles when they were released, but they should have served time with adults.”
The 25th anniversary comes in the same week that Venables was again sent back to prison for 40 months for having a number of indecent images of children. It is the second time he has gone back to prison.
"Venables has remained in the public spotlight due to his further convictions, but Thompson slipped back into society, never to be heard of again.
Mr Roberts, who now enjoys retirement by helping out with the local bowling and football club in Llanrhaeadr, is not surprised Thompson went to ground.
He said: “It doesn’t surprise me we never heard from Thompson. He was calm, he lied and we could pick up on it, but he was calm, street smart.”
Mr Roberts had worked on serious crimes and murders for 24 years before the notorious case of James Bulger.
He added: “I worked on murders throughout my service, you learn to stay straight-faced and show no emotion.
“But there is a moment when you sit and think has that just happened, and how could these boys have done something so horrific.”