A SEX offender who dragged a sleeping teenager into a train toilet and sexually assaulted her was found guilty on Monday.

John Diddier, 49 and of no fixed address, was found guilty of assault by penetration and two charges of sexual assault by a jury of eight men and four women at St Albans Crown Court.

And it was revealed that Diddier had previously been convicted for two cases of indecent assault on women on trains in 1992 and another indecent assault in 1984 on a sleeping female patient at a hospital in Newham, London.

The 17-year-old victim, a student from St Albans, had fallen asleep and missed her stop on a train that had left St Pancras Station at 4.50am on January 26.

She fell asleep just after Radlett and missed her stop in St Albans, waking up at the end of the line in Bedford.

The train was due to return to London at 6.18am so she stayed on it in order to get home but while she sat on the train dozing, Diddier tried to talk to her.

Prosecutor Janet Weeks told the court how Diddier had started stroking the girl’s arm and she had pulled it away, asking him to stop touching her.

The victim, scared and alone with Diddier in the carriage, was then pulled into a toilet cubicle and he began to kiss her.

Ms Weeks said: “She said ‘stop’ but he did not listen. He was slobbering. She said ‘stop’ a number of times.”

Diddier then pulled down the teenager’s pants and sexually assaulted her before crouching down and biting her.

Ms Weeks added: “Nothing was said by him, but after a few minutes he dragged her out of the toilet and pushed her back to the same seat. He then leant towards her and pulled up her dress and fondled her breasts.”

The girl pleaded with him and he told her that next time he wouldn’t stop.

After the attack, two men got into the carriage and she went and sat by them. Diddier appeared and asked why she had moved. One of the men then told him to leave her alone as she was clearly upset.

The teenager got off the train at St Albans at 7am and went home. Later that morning she reported what had happened at St Albans police station.

DNA on her bra, dress and pants was found to match Diddier.

He was arrested and gave a no comment interview. His case was that the girl consented and he denied all charges against him. After conviction, the jury heard of Diddier’s previous convictions and that he’d appeared in court 24 times for 70 offences.

The majority were not sexually related but previous cases of indecent assault were revealed. After assaulting the hospital patient in 1984, Diddier also masturbated in the nurses’ quarters.

He was unanimously convicted of assault by penetration and one of the sexual assault charges. The jury convicted him by a majority of 10 to 2 on the other charge of sexual assault.

Judge Marie Catterson adjourned sentence for reports from probation officers on the danger Diddier is to the public. She remanded him in custody.