A former sacristan for the Knights of Malta has pleaded guilty to nine sex offences including those against boys as young as 11 he had met in the 1960s and 70s.

Vernon Quaintance, a companion of the Order of Malta, served at the Knights’ regular Mass at the chapel in St John and St Elizabeth Hospital in North London.

On Wednesday this week a court heard that Quaintance, 71, was a paedophile who also ran a pro-circumcision group. Southwark Crown Court heard he accumulated images as recently as 2011.

He was also a leader of the Gilgal Society, a group claiming to promote male circumcision and “its benefits in terms of health, sexual satisfaction and self-image.”

In 2012, he was found guilty of possessing nine hours of child pornography on video tapes. This week he pleaded guilty to five counts of indecency with a child between 1966 and 1976 and four counts of possession of indecent images. An additional count of sexual assault alleged to have taken place in 2011 on a child was left to lie on file.

Judge Anthony Leonard QC adjourned sentencing until September. He said there was a “very real likelihood” of a significant custodial sentence. Quaintance was released on conditional bail, with the requirement to have no unsupervised contact with anyone under 18.

Concerns about Quaintance’s behaviour had come to the attention of members of the Grand Priory, a senior body of knights, who were later found not to have reported the concerns to the relevant authorities. Quaintance had been banned from serving and attending the social club at St Bede’s, Clapham Park, South London.

An inquiry into the matter by Baroness (Julia) Cumberlege found that three of the knights made a catalogue of serious errors in dealing with the concerns. The three later apologised.