Russell Bishop has been branded a "cowardly" paedophile who has spent most of his adult life in denial over the Babes in the Woods murders.
Prosecutor Brian Altman QC described him as "an abusive, aggressive, controlling man" who was capable of "extreme sexual violence".
But when called to account for his crimes, the 52-year-old predator hid behind "cowardly" lies and even cast himself as the victim before refusing to carry on, Mr Altman said.
Growing up in Brighton on the south coast, Bishop was Sylvia and Roy Bishop's youngest of five sons.
Mrs Bishop, described in court as a "domineering" matriarch, is a successful international dog trainer and author of the instructional manual It's Magic.
Bishop's roofer father was wrongly suspected in 1978 of being the Beast of Stanmer Park.
Mr Bishop senior had been arrested but never charged over the unsolved murder of Brighton woman Margaret Frame, who was buried in a shallow grave.
Fearful of history repeating itself, he even warned his son not to get involved in the search for the missing girls in 1986, the court was told.
As a youth, Bishop struggled with dyslexia, and he told jurors he had difficulty reading and writing and with "problem solving".
At 5ft 5in and weighing just over 10 stone, in 1986 Bishop sported a moustache and was said to be charming.
He lived with his partner Jennie Johnson and their infant son Victor in Stephens Road, Brighton, while also carrying on a relationship with 16-year-old Marion Stevenson, who was "besotted" with him.
Bishop and Ms Johnson were said to be keen CB radio users, going under the handles "Silver Bullet" and "Panda Bear".
While Ms Johnson worked as a cleaner at American Express, Bishop variously held down jobs as a roofer and turned to petty theft and motoring crime.
In her evidence, Ms Stevenson suggested he had attacked Ms Johnson several times, knowing she was pregnant with their second baby.
He was said to be "motoring mad" and would spray-paint cars in his spare time, as well as playing football in the park, night fishing and smoking cannabis.
Bishop was rounded up by police investigating the IRA Grand Hotel bombing in 1984 but was soon discounted as a serious suspect, the Old Bailey heard.
He knew both Nicola Fellows and Karen Hadaway's families and the girls were befriended by Ms Stevenson.
Bishop, who went on to have three children, was just 20 years old when he crossed the line from petty thief to violent paedophile.
Even before the murders, his behaviour towards young girls was a cause for concern.
The court heard how he had lusted after girls doing handstands in the park, saying "wait until she is 13 or 14".
He also got to know an 11-year-old girl in 1985, who he went on to groom for sex in a series of letters while he was in prison awaiting trial two years later.
In childish handwriting, he peppered his love letters with hearts and kisses, while bragging about his sexual prowess, warning the girl he was "a man not a boy".
On his release, Bishop faced a barrage of animosity in the community, with windows smashed and petrol put through the letter box.
He claimed he became mentally ill as a result and even considered throwing himself off Beachy Head with his children in tow.
In 1990, he decided he "might as well" do what he had been accused of, and snatched a seven-year-old girl, he told jurors.
Bishop denied he was a paedophile, and claimed he acted out of vengeful rage and wanted to "belittle and shame her" when he attacked her at Devils Dyke.
But Detective Superintendent Jeff Riley, who led the cold case investigation, said: "I think his evidence summed him up, didn't it? Wicked.
"He wanted to shame and humiliate her. What a wicked thing to say. To think that was a defence to what he did beggars belief."
Since his incarceration, Bishop has been left in a time warp as a category A prisoner with little or no experience of the world.
He piled on the pounds and pumped iron as he first launched an appeal, then applied for release from the parole board, all without success.
At the time he was ordered to face a retrial for double murder, he was an inmate of HMP Frankland in Durham.
On the day of his arrest for the 1986 murders, he was moved without explanation from jail to a police station.
Mr Riley said: "We arrested him for the murders of Karen and Nicola. That would have been when the penny dropped. He just wanted to go back to prison and just did not want to be there."
On the character of the killer, he said: "I think there is an arrogance about him without doubt. He is massively dishonest."
On the risk he poses to society, the senior Sussex Police officer said: "I think the fact he is 14 years over his original tariff, he is a category A prisoner, says how dangerous he is."
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