A former Olympic gymnastics judge has been jailed for sex abuse after a private detective used the Internet to trace his victims.

Ron Smith, 65, of Wessex Road, Didcot, was sentenced to three years in prison at Oxford Crown Court yesterday for offences committed more than 20 years ago.

Smith, a former teacher at an Oxfordshire school and after-school gym instructor during the 1980s, was found guilty of five charges of indecent assault on a male under 14 and one of indecency with a child under 16. He was found not guilty of three more charges of indecent assault on a male under 14.

Rachel Drake, prosecuting, said investigations began six years ago after allegations were made about Smith's behaviour towards a young boy during the 1970s.

The allegations were not enough to make a case, she said, but the British Gymnastics Association hired a detective who used the Friends Reunited website to contact other people coached by Smith when they were children. She said: "It was through his efforts that the first two complainants in this case came forward."

During the trial, the court heard about incidents between 1982 and 1986 involving three victims aged between 10 and 13 at the time.

Smith, who was a judge at the 1984 Los Angeles Olympics, took them on weekend trips, during which they would camp and stay in youth hostels or at Smith's flat in Bath.

The court was told that the boys, who were given beer and shown pornography, were made to share his tent and, on one occasion, his bed, where he sexually assaulted a boy.

Smith told the court he may have slept in tents with boys, offered them a sip of beer and they might have seen one of his top shelf magazines by accident, but denied all indecent assault charges.

He said: "When I think about all these events and allegations it's like looking through a kaleidoscope and trying to find a pattern - but I cannot."

After the guilty verdicts, Miss Drake told the jury that Smith had been found guilty of indecent assault against two 12-year-old boys and fined £20 in 1969.

Smith was given permission to continue teaching after writing to the then Education Secretary, defence barrister Andrew Lamden explained.

Judge Julian Hall, who read letters from former pupils and young gymnasts, said: "It is quite clear that you have made a most positive contribution to the lives of many children, particularly in the field in which you are a specialist, but you abused the trust of some of them."