A private detective has described the part he played in a six-year police investigation into a former teacher and paedophile.

Phil Lewis spent months searching for former pupils from Oxfordshire who had come into contact with the former Olympic gymnastics judge Ron Smith, jailed for three years on Wednesday after a trial at Oxford Crown Court.

Smith, a 65-year-old from Wessex Road in Didcot, was found guilty of indecently assaulting boys under 14 and indecency with a minor - all crimes committed in the 1980s.

Thames Valley Police began investigating Smith in 2000 after a man claimed he had been sexually abused by him in the 1970s.

Because Smith denied all the allegations, the investigating officers had to try and find more evidence and the British Gymnastics Association asked Mr Lewis for his help.

A former police officer from Gloucestershire, Mr Lewis spent months trawling through the phone book and websites, such as the Friends Reunited site, to find other potential victims.

He said: "The reason I kept going when I got no responses was because I believed the original complainant and I was sure there was going to have been systematic abuse of young children.

"It took several months, and God knows how many hours I spent on it."

The names the private detective handed to Thames Valley Police, along with the evidence of victims they had collected themselves, was enough to send him to jail.

Dc Mark Jenkins, of Thames Valley Police, worked on the case from when the first victim was interviewed in 2000 right up until this week's conviction.

He said: "An important piece of information about one of the victims was passed to us by a private detective which we followed up and we then identified two further victims.

"We are pleased with the outcome of the trial and hope that this helps to bring closure for his victims."

In court, it emerged that Smith had earlier convictions for indecently assaulting two 12-year-old boys during a swimming trip in the 1960s.

Fined £20 for the offence, Smith was nevertheless allowed to return to teaching after writing to the then Education Secretary.

Mr Lewis said: "What horrified me all the way through was that he was convicted in 1969 and the Government allowed him to go back to teaching and continue his abuse."

Following this week's conviction Smith has been placed on the sexual offenders register for life.

Mr Lewis added: "With all the publicity around the case, I would be very surprised if there aren't more complaints."