Viewers have been gripped by ITV’s three-part drama based on the memoirs of former Met police detective Colin Sutton, whose investigation into the brutal death of Amélie Delagrange led him to connect her killer to the murders of Marsha McDonnell and Milly Dowler.

East Anglian Daily Times: Former Met police officer Colin Sutton Picture: SUPPLIED BY COLIN SUTTONFormer Met police officer Colin Sutton Picture: SUPPLIED BY COLIN SUTTON

The ex-detective chief inspector, played by Martin Clunes in Manhunt, gave Levi Bellfield’s name to the Surrey police team investigating 13-year-old Milly Dowler’s murder in 2002.

Mr Sutton, 58, now a national media consultant, began writing while still in the force, but put down his pen and left his book unfinished until retiring in 2011 and moving to Suffolk, where he later went on to be a candidate for police and crime commissioner.

After consulting on another project, he was encouraged to continue by Ed Whitmore, who later phoned to say a production company was interested in the still unfinished book, leading them to collaborate on the first episode, which got the series commissioned in 2017 and sparked a “mad rush” to write two more episodes and the rest of the book.

“We agreed we wanted it to be really authentic, in terms of the language, setting and accuracy around the investigation,” he said.

East Anglian Daily Times: Metropolitan Police photo of Levi Bellfield Picture: METROPOLITAN POLICEMetropolitan Police photo of Levi Bellfield Picture: METROPOLITAN POLICE

“The only compromises were that we couldn’t include everyone, or we’d have a cast of about 80 people, and we slightly shuffled the order to make it flow better.”

While many critics have praised the drama’s sensitive portrayal of events, for some, the recreation of a murder scene on Twickenham Green took authenticity to excess.

Mr Sutton said: “Yes, there has been some controversy about the locations, but none of that came from the families themselves. It’s another case of people being offended on behalf of others.

“Watching it reinforced how well it was done, and brought back emotions I felt at the time. Going to France to see Amelie’s parents was one of the most difficult things I’ve done.

“As soon as I knew the programme might be happening, I wrote to all concerned. Had they asked me not to go through with it, I wouldn’t have.”

Mr Sutton followed his father and grandfather into the police in 1981 and ended up in charge of some of the most high-profile Met cases, including 37 murders in nine years.

After Bellfield’s arrest, the Met investigated about 20 other alleged offences, including sex assaults.

Police believe he tried to abduct another girl three miles from where he snatched Milly Dowler a day later. With hindsight, they said what happened was more significant than first thought and was a “missed opportunity”.

Mr Sutton said: “It’s pretty plain he could have been caught earlier.

“Mistakes were made, but in the context of a small, stretched force, dealing with two other major investigations.

“I’m never too hard on people, not because some were colleagues, but because we were dealing with a cunning man, who was aware of what he could do to minimise his chances of being caught.

“I believe it’s accurate to describe him as evil. He’s up there with [Peter] Sutcliffe and [Fred] West. The most egotistical, self-centred person I’ve come across.

“I’m convinced others were assaulted, seriously and sexually, but murders and unexplained deaths are taken so seriously that they’re less likely to go under the radar and not be connected.

“Common sense says he didn’t just reach his 36th birthday and decide to start committing crime. I’ve had two or three people, who we didn’t already know about, approach me on social media since the programme started.”

In January 2016, Mr Sutton ran for police and crime commissioner (PCC) but withdrew as an independent candidate due to other commitments. He now admits the decision was partly due to politics, and he still has strong opinions on the impact of funding cuts and on police forces.

“Officers are overworked, and there are probably fewer of them than in my day, but I would hope resources are always still found for major investigations,” he said.

“That shouldn’t disguise that we are really on the edge. Officers are not finding it easy to cope. Any more cuts, and that trickle of discontent could turn into a flood.

“I believe the role of an independent PCC is an excellent one. The problem is, it’s a party politicised job. I simply didn’t think I could win.

“Did I think I could do the job? Yes. But, short of selling a kidney, I couldn’t take on someone with parliamentary campaign support.

“That sounds like I took my bat and ball home, but my reason for withdrawing was also because of other commitments – one of which we’re seeing on ITV at the moment.”