PROLIFIC Exeter offender William Roast has now added a sex offence to his record of more than 100 crimes.

The 40-year-old, whose official address was given as Exeter Prison, was yesterday jailed for 25 months at Exeter Crown Court.

He pleaded guilty to sexual activity with a child under 18 and an offence of witness intimidation.

Prosecutor Gareth Evans said that Roast had drunkenly committed the offence when he was alone with a girl from Devon in 2008.

An adult found out what happened and alerted police after Roast told them: "I didn't do nothing."

Mr Evans said: "In interview, he was to deny totally any contact and maintain this stance until the day it was listed for trial."

Mr Evans added that Roast has a record of 104 crimes, including violence, having a blade, possessing amphetamine, burglary, driving offences and handling stolen goods.

The witness intimidation offence involved putting pressure on the adult who had already reported him to police.

The defendant began committing crimes in 1984 when he was a youth. His last offences were in 2008.

Defence counsel Nicolas Gerasimidis said Roast had made good progress in prison including tackling his drug use.

He added: "Although heavily convicted, he has no previous convictions for sexual offending."

He said the sexual offence was not the most serious type of physical activity.

"The witness intimidation followed the anxiety caused to Mr Roast at a time when he was confused as a result of alcohol and drug problems," said Mr Gerasimidis. "This type of offending is very unlikely to reoccur."

Judge Philip Wassall put Roast on the Sex Offender Register for life and imposed a Sexual Offences Prevention Order.

He told Roast: "You have pleaded guilty very late in the day."

The judge praised the bravery of the adult who alerted police about the offence.

He said: "You have pleaded not guilty right up until the day of the trial. You sought an indication from me about possible sentencing on the day of trial and pleaded guilty.

"You have no previous convictions for sexual offences but have a long criminal record. The probation service has assessed you at high risk of reoffending."

Roast has pleaded not guilty to three offences of criminal damage, which the prosecution successfully applied to lie on file. He had also denied affray for which the prosecution offered no evidence.