A 13-year-old girl was handcuffed and raped by a pervert and his infatuated teenage girlfriend.

Stephen Stock, 24, and his girlfriend Paula Payne are today behind bars for carrying out a horrific sex attack on their young victim who they threatened to kill.

Police believe the attack was part of a sick fantasy to rape a virgin which the couple had plotted and which Payne, aged 16 at the time, had written down in an exercise book before choosing their victim.

Entitled The Plan, the book discovered by detectives revealed chilling details of sexual abuse on a young girl.

In a case which police said would have shocked the hardest of officers, Lewes Crown Court heard how the couple lived out their fantasy on March 12 last year after befriending the victim.

Stock forced his victim to have sex while Payne helped him. Payne handcuffed the victim's hands behind her back and blindfolded her before cutting off the girl's top and bra.

The terrified victim was threatened she would be killed during the sickening ordeal which lasted hours.

Stock, of Ashton Rise, Brighton, was yesterday jailed for nine years after admitting rape. Payne, now 17, of Seaview Estate, Southwick, admitted aiding and abetting rape and was sentenced to three years in a young offenders institution.

Gill Etherton, prosecuting, told the court the victim was a virgin with no sexual experience before the attack.

The girl spent the evening with Stock and Payne at Stock's mother's home in Seafield Road, Hove. They brought ingredients to make cakes and watched DVDs but when she tried to leave they refused to let her.

Ms Etherton said Stock became angry and aggressive. He grabbed her around the neck and a pillow was put over her face to stop her screaming.

Ms Etherton said the girl was terrified but Stock told her not to worry as he had done this before. She said: "Stock told her they had planned this for ages and now it had worked out."

During the sexual attack Stock repeatedly threatened to kill her.

Ms Etherton said: "Throughout this ordeal she was very scared. She really thought Stock meant what he said about the threats.

"She described how Payne played an active role assisting Stock and instructing him what to do and watching the acts take place."

She said The Plan found by police set out the rape of a young girl and included chilling details.

After the sex assault was over, they instructed the girl to shower but she was not allowed to leave the house until the following morning. Again she was threatened if she told anyone and this time she was warned she and her sister would be killed.

The following day Payne visited the girl at her home where she forged a note excusing the victim from school because she wanted her to attend her GP to get a morning-after contraceptive pill.

The next day the girl broke down to a friend who she showed her injuries on her neck and wrists. A teacher was told and the police began an investigation. The girl is still suffering from her ordeal, feeling scared to go out and often crying.

The court heard Stock and Payne had been in a relationship since she was 13 and he was 21 and had a child together when she was 14 who was taken into care and has been adopted.

Stock has no previous convictions, but has cautions all related to incidents involved Payne, including for under-age sex, resisting arrest and common assault on a social worker.

But the relationship is now believed to have ended. The couple stood feet apart in the dock and did not make eye contact. Neither showed emotion during sentencing.

Judge Charles Kemp told the couple: "This was the most appalling and disgusting incident. That utterly defenceless young girl must have been nothing short of petrified."

He said to Payne she was infatuated by Stock and their relationship had damaged her life. He said: "I am satisfied you played a full and compliant part in this offence. Instead of helping that girl you assisted Stock in achieving his purpose. I have no doubt you need help and guidance."

Paul Casey, defending Stock, said he was immature for his age.

Richard Barton, defending Payne, described her as a vulnerable young victim herself because of her abusive relationship with Stock. He said Payne had written down Stock's sexual fantasy in the book not because she was innately evil but because she was being groomed by her boyfriend.

DC Chris Leech, who led the investigation, said: "Rape is one of the worst crimes but in this case there are factors which make it even worse, such as the girl's age and lack of sexual experience plus the fact someone she trusted of her own sex that she thought was a friend led her into the most awful experience of her life."

Stock will have to sign on the sex offenders register for life and Payne for ten years.