An 80-year-old Otley paedophile has five convictions for indecently assaulting under-age girls - but has never served a prison term for his sex crimes, the Old Bailey heard yesterday.

The revelations about former dentist Trevor Mellis, pictured, emerged as he awaited sentence with three other men after police smashed a paedophile ring responsible for publishing a guide book on how to groom children for abuse.

Mellis has admitted three counts of taking indecent photographs of children under 16 and one count of distributing indecent photographs.

Sentencing was adjourned until Monday but the court heard that Mellis had committed a catalogue of sex crimes for which he had never received more than probation.

While lawyers for the other three defendants accepted their clients would receive custodial sentences, Mellis's legal team argued for a suspended sentence because of his age, ill health and because the offences were committed 18 years ago.

Adjourning sentencing, Judge David Paget QC said: "The fact I remand all the defendants in custody does not mean that is the final outcome for all the defendants."

Mellis's string of convictions began on April 10, 1964, when he was convicted in Leeds of three offences of sending obscene material in the post and fined £15.

The following year, also in Leeds, he was convicted of indecently assaulting an 11-year-old girl and sentenced to a fine of £20.

After that he was struck off the dental register.

He received another £30 fine at Leeds for publishing obscene material on another occasion.

Then, on April 23, 1974, he was convicted of four counts of indecent assault - three of them were on a girl aged ten and one on a girl aged eight. He was sentenced to two years probation.

The arrest of Mellis and the three other defendants followed an operation by the Metropolitan Police which recovered thousands of pictures and hundreds of videos and magazines showing young children being abused.

They raided the home of Keith Romig, 55, in April 2000 in east London. Romig has pleaded guilty to one count of indecent assault of a girl under 13, one of conspiracy to distribute indecent photographs of children, one of taking indecent photographs of a child under 16 and one of making an indecent photograph of a child under 16.

Julian Levene, 58, was arrested shortly afterwards at his home in Middlesex. He has pleaded guilty to one count of unlawful sexual intercourse with a girl under 13, one of indecent assault of a girl under 13, five indecent assaults on females unknown, one of taking indecent photographs of a child and one of conspiracy to distribute indecent photographs of children. Also arrested was Leslie Baldwin, 51, of Kensington, west London. He has pleaded guilty to four counts of indecent assault on a child under 16, four of taking indecent photographs of a child under 16 and two of distributing indecent photographs of a child under 16.

In mitigation for Mellis, barrister Justin Rose said: "The defendant is 80 years old and he is a very sick man. His age and infirmity are such that the risks of re-offending are remote."