The reality is if you were to have a television programme that looked at how murders were really investigated, it would be the most boring show on TV.

To show how open-minded detectives must be when they first arrive at a crime scene, Steve talks about a double murder at a flat in West Norwood, south London, in October 2009. He was commended for his role in investigating the 7/7 bombings during which he crawled through tunnels collecting body parts. The same is true for those said to have died at his hands. If Polly Nicholls, Annie Chapman, Elizabeth Stride, Catherine Eddowes and Mary Jane Kelly had not fallen to his knife, their names would have been lost to history. Instead, they themselves are as much a part of the folklore as their killer. Then there are those who investigated the the ordinary men, doing their jobs as best they could, who will always be associated with the failed attempts to catch this monster.

After retiring from the police in 2021, Steven created 'Murder Academy', the world's first school dedicated to educating true crime fans on how murders are solved. Steve writes: 'However unlikely, it was the only lead we had with a possible motive and the decision was made to arrest the 14-year-old boy on suspicion of murder.' Part Four provides a high-level review of suspectology. Mr Keogh suggests criteria that might be used to eliminate suspects who were in fact innocent. He applies the criteria to ten popular suspects and considers eight of them eliminated. During my time on MITs, those dreams started to become more and more violent in nature. Most nights I would end up killing someone in my sleep. Stabbing, shooting, beating or strangling." Seeing the post-mortem examination of Daniel Evbuowman, three, who was battered to death by his uncle Ben Igbinedion, 51, just for wetting the bed in 2013 was also a sight he "could not unsee."

Gang members believed Samuel was going to snitch during a firearms trial and Ola Apena, of south London, arranged Samuel's murder from within an Oxfordshire prison using illicit mobile phones. Boy, 15, and man, 23, are knifed to death in Islington double murder as music video shoot turns to mayhem and third victim, 28, is rushed to hospital with stab wounds

Toys

Former Detective Inspector Steven Keogh joinedthe Metropolitan Police in 1991, spending most of his 30-year career as a detective.