A "bullying, controlling, violent" pervert has been sentenced to life imprisonment for the systematic rape and abuse of two young sisters. He fathered two children by one of his victims, kept her prisoner in a flat and had complete control over her. Unemployed Peter Tweed, 47, from Ramsey, pleaded guilty to 22 charges: 13 counts of rape, six counts of indecency with a child, two counts of indecent assault and one charge of assault on a boy. He denied four charges of rape and illegal sexual intercourse, which were ordered to lie on file. All the charges related to when the girls were under 16, although the court heard the systematic rape and abuse continued long after that. Tweed, who lived in another Huntingdonshire town at the time of the offences, bullied his child victims into becoming his sexual playthings, even forcing them to have sex together to fuel his sordid fantasies. On Monday, Peterborough Crown Court heard how Tweed started abusing the girls in 1976 when the youngest was 12. Yesterday (Tuesday) he received a life sentence from a judge who told him that what he had done "defies belief". The court heard how Tweed had vicious nicknames for the two sisters calling them "slag" and "bitch". William Redgrave, prosecuting, said Tweed rented hard core videos and made the girls watch them. One girl eventually escaped his clutches at the age of 18 but the other was forced to continue having sex with him into her mid-30s. He fathered her two children. Tweed kept her a prisoner in a council flat, visiting her every other night. When he left, he would lock her and her children inside, taking the keys and taping around the door frame so he knew if she had tried to go out. Mr Redgrave said Tweed even set up CB radio between his home and the flat and called at all times of the night to check she was in. His sickening crimes only came to light after his victim lost 10 stone through a slimming club. She gained the confidence to contact her sister for the first time in 20 years and together they decided to trap their tormentor. The sister still in his power hid a tape recorder in the flat before staging an argument with Tweed, during which she forced him to confess what he had done to her and her sister throughout their teens. Mr Redgrave told the court: "Peter Tweed was a bullying, controlling, violent figure who coaxed the girls into committing acts of increasing sexual depravity." He said one of the girls "had been conditioned and bullied into becoming a sexual plaything and had no chance of getting out of that lifestyle. "The sexual behaviour he expected from her became exceptionally violent... and any sensible description of this activity as consensual is unrealistic. "Any spirit she may have had was crushed out of her. She became a sexual plaything and a puppet for him to act out his increasingly unpleasant sexual desires on. The objects used became increasingly too unpleasant to contemplate." Mr Redgrave said Tweed told the girls to prove that they loved him and told them he was bringing them closer together by forcing them to have sex with each other. He would often wield a leather belt to hit the girls and told them they must never tell anyone what happened. Throughout the eventual police investigation, the court heard how Tweed saw himself as a victim, even taking an overdose before his trial was due to be heard. Judge Nicholas Coleman told Tweed: "The conduct you showed to both girls was repulsive. In my judgement what you did defies belief. "Fortunately, one of the girls was able to escape your attentions but no such future awaited the other. She was effectively colonised by you. She was unable to look after herself until well into her mid-30s. "It was persistent abuse of two young girls as your sexual playthings for many years. You ruled by fear. It's impossible to imagine the long term effect on these two young ladies. "Your conduct demonstrates persistent perverted tendencies and in my opinion personality disorder." He sentenced Tweed to life for the 13 rapes with a tariff of 13 years and a recommendation he serve a minimum of six-and-a-half years. He sentenced him to three years for the indecent assaults, three years for the assault and 18 months for the indecency charges, all to run concurrently. Tweed was also ordered to sign the sex offenders' register and banned from working with children. John Lloyd-Jones, defending, said: "Mr Tweed has no recollection of events prior to 2005 when he took an overdose and given the nature of the incidents I have very little to offer in the way of mitigation." He said Tweed had claimed to have loved one of the women since she had been a child and he was subject to depression. Detective Constable Richard Croft, who led the police investigation, said: "Tweed inflicted the most horrific abuse on his victims, depriving them of their childhoods and tarnishing their lives forever. "His depraved crimes and systematic abuse of his young victims make him a very dangerous man "I hope the women he abused as children will now be able to rebuild their lives with the support of their friends and family.