A PREDATORY paedophile who plied a boy and girl with alcohol and cannabis to maintain sexual relationships with them will stay in jail until he is no longer a risk to children.

Judge Tom Corrie said former schoolmaster Michael Costin posed a serious risk to both young boys and girls following the convictions, which came 15 years after he was jailed for similar offences against Sea Scouts under his command.

Costin, formerly of Abingdon, was told he must serve at least five years behind bars before the parole board could consider him for release.

The judge told the 46-year-old: “You provided these young people with what must have been a teenager’s dream: somewhere where they could drink and take cannabis. You were very careful while encouraging them to overindulge not to do so yourself, so to exploit them.”

Costin was caught when he was repeatedly spotted outside a school in Abingdon, and an investigation was launched.

It emerged he had been having consensual sexual relationships with a boy from when the youngster was just 13-years-old and then with the girl – the boy’s girlfriend – when she was also underage.

After a trial at Oxford Crown Court a jury convicted Costin of seven counts of sexual activity with a male child under the age of 16 and four counts of sexual activity with a girl under the age of 16. The charges ranged in date from July 2007 to last year.

He was also found guilty of sexually assaulting a 17-year-old boy, who he tried to masturbate in a vehicle outside Millwall Rugby Club, in East London. He had previously been chairman of the club and was expelled following his arrest.

Costin was cleared on two counts of raping the younger boy.

Rachel Drake, prosecuting, told Judge Corrie that on May 21, 1996, Costin was convicted at Ipswich Crown Court, Suffolk, on four counts of indecent assault.

“Those offences related to three different adolescents who came into contact with the defendant because he was a teacher and was a leader of the Sea Scout troop to which they belonged,” she said.

For those attacks Costin was jailed for two years and placed on the Sex Offenders’ Register for 10 years.

Lauren Soertsz, defending, said Costin had not forced any of the children in the latest charges into doing anything.

Judge Corrie said Costin had created a distorted reality in which the children had considered it normal to act in such a way.

He said: “There can be no doubt you corrupted these susceptible teenagers by providing them with the cannabis and alcohol for facilitating your abuse of both.

“I have no doubt that you are a predatory paedophile.”

He passed an indeterminate sentence for the public protection on Costin, now of Lincoln Avenue, Romford, Essex, with a recommendation he spend at least five years in jail.