Many hundreds would be a modest estimate of the number of young boys with whom Alan Doggett was allowed close contact after his suspected abuse of a pupil came to the attention of St Paul’s School.

Quietly removed from his post at Colet Court, the future member of the Paedophile Information Exchange (PIE) went on to teach boys at a second independent school before working as a choirmaster with boys from more than 30 London schools.

A decade after his departure from Colet Court, the 41-year-old threw himself in front of a train a few hours after appearing in court, accused of twice indecently assaulting a child aged 10. Doggett’s bail conditions barred any further contact with his choirboys.

In the 17 years preceding his 1978 suicide, he worked almost daily with pre-adolescent boys. He was a gifted but weak man, surrounded by temptation.

Doggett was a former pupil of Colet Court and St Paul’s who returned to the prep school as director of music from 1963 to 1968, having previously taught the cellist Julian Lloyd Webber at Westminster Under School, the junior division of Westminster School.

A regular guest at the Lloyd Webber household, he became friendly with Julian’s elder brother, Andrew, and in the summer of 1967 invited the fledgeling Tim Rice-Lloyd Webber songwriting partnership to pen a pop cantata for an end-of-term school concert.

Rice was then 22, Lloyd Webber 19, and from that invitation Joseph and the Amazing Technicolor Dreamcoat was born. Its first performance was in March 1968 at Colet Court. Four months later, Doggett conducted the first recording of Joseph, at EMI’s Abbey Road, again featuring boys in the prep school choir.

Allegations of sexual misconduct with a pupil led to his dismissal in the same year but by 1969 he was again teaching music to boys, this time at the City of London School.

Doggett’s association with Rice and Lloyd Webber continued until 1976. He was principal conductor on the original recording of Jesus Christ Superstar and directed the London Boy Singers — a choir whose first president was Benjamin Britten — in his role as “musical co-ordinator” for the first Evita album. As the choir’s reputation grew, he took his boys on European tours. They performed for the Pope, appeared on radio and television, recorded albums and performed in films. Doggett’s death came 15 days before he was due to conduct a massed choir of 1,000 schoolboys — all personally selected and coached — at the Royal Albert Hall. Police had been planning to interview every boy.

A farewell letter explained that in life he had chosen “the way of the Greek”, which “though hard is best”. Days later, Rice and Lloyd Webber issued a joint statement: “Alan was a music and singing teacher of extraordinary talent. We have lost a gifted colleague and a dear friend.”

Rice spoke at the funeral. In his 1999 autobiography, he wrote: “I cannot believe that Alan was truly a danger, or even a minor menace, to the many boys he worked with over the years. It has been known for young boys . . . to manufacture or exaggerate incidents when they know and disapprove of a teacher’s inclinations.”

Lloyd Webber was said by a biographer to remain convinced that “Doggett would never have been guilty of taking advantage of any young person in his charge”.

After his death, an edition of Magpie, the newsletter for the PIE pressure group that campaigned on behalf of paedophiles, revealed that a requiem Mass was said for Doggett by a Catholic priest, Michael Ingram, at a church in Leicester. Twenty-four years later, in 2002, Ingram was convicted of multiple sex offences between 1970 and 1978 against six boys aged from 9 to 12.

PIE’s treasurer, Paul Andrews, wrote that Doggett killed himself after being “accused of indecency with a 10-year-old boy”, adding that he could “well imagine the innocence with which this act of love and affection had taken place”.

Ian Pace, a professional pianist, City University lecturer and campaigner against abuse in musical education, last night demanded a “proper investigation” of Doggett’s continued access to boys after his offending was first exposed at the prep school. “It is rare for such abusers to have merely a few isolated victims,” he said. “The potential implications of this are alarming.”