A man was sentenced to life in prison Friday for plotting to kidnap, rape and murder Holly Willoughby, one of Britain’s most high-profile television personalities, in a case that an undercover Minnesota police officer helped crack.

At the sentencing hearing at Chelmsford Crown Court, around 40 miles east of London, Judge Edward Murray told Gavin Plumb, 37, that he would have to serve a minimum term of 16 years before he can be eligible for parole.

Plumb was found guilty by a jury last week following an eight-day trial.

“Over a number of years, you pursued an unhealthy sexual obsession with Holly Willoughby that led you ultimately to plan over that period to kidnap, to rape and to murder her,” the judge said. “You intended to harm her husband and her children as part of your plan.”

Plumb’s kidnap plans, as fleshed out in vivid detail in an online chat group, involved attempting to “ambush” Willoughby at her family home. He had even discussed taking time off work in order to organize the attack.

The judge said Plumb’s plans were so “horrifying, shocking and graphic in detail” that they were not shared in open court, though the jury did hear them.

They were, he added, “particularly sadistic, brutal and degrading” and he had no doubt the plans were “considerably more than a fantasy.”

Plumb, who had prior convictions for attempted kidnap, had argued in his defense that his detailed plan was just online chat and fantasy.

Though Willoughby’s impact statement was not relayed, the judge said it was clear that Plumb’s plot had a “catastrophic and “life-changing” impact on the TV personality, privately and professionally.

Willoughby, 43, has for years been one of the most high-profile television personalities in the U.K. Soon after Plumb’s arrest, she stood down after 14 years in her role presenting “This Morning,” a magazine program on ITV that mixes celebrity interviews and entertainment news with discussions about current affairs. She did return to co-host the channel’s “Dancing on Ice” earlier this year.

“I’ve never seen such a skilled detective”  

Plumb was snared after an undercover Minnesota police officer infiltrated an online group called “Abduct Lovers” and became so concerned about Plumb’s posts that evidence was passed to the FBI.

Plumb told the officer, who was using the pseudonym David Nelson, that he was “definitely serious” about his plot to kidnap Willoughby, leaving the officer with the impression that there was an “imminent threat” to her.

U.S. law enforcement in turn contacted their counterparts in U.K., and when Essex police officers raided Plumb’s flat in north London they found bottles of chloroform and an “abduction kit” complete with cable ties.

Jeff Mundale, Owatonna’s police chief, told CBS Minnesota that his detective needed just two days of messaging and building trust to get the information he needed to decide to alert the FBI and British police.

“In my 29 years of serving law enforcement, I’ve never seen such a skilled detective in engaging in this sort of work,” said Jeff Mundale, Owatonna’s police chief. “It’s certainly impressive.”

When Plumb was arrested and officers told him that the allegations concerned Willoughby, the defendant told them: “I’m not gonna lie, she is a fantasy of mine.”

Willoughby waived her right to anonymity in connection with the charge against Plumb of assisting or encouraging rape. In the U.K., alleged victims of sex offenses or targets of sex offense conspiracies have a right to automatic anonymity for life from the moment an allegation is made by them or anyone else.

Detective Chief Inspector Greg Wood, of Essex Police, the senior investigating officer, said the case “brought misogyny and violence against women and girls to the fore” and paid tribute to Willoughby and others

“It has demonstrated that we all have much to do to stamp it out of society,” he said outside of the court following the sentencing. “It cannot be right that men like Gavin Plumb are able to join online forums where they freely vent their hatred towards women and girls and plot to cause them harm. We need everyone to stand up and call out misogyny and to report those causing violence towards women and girls.”