The men, two of whom were superintendents, were charged after a cadet came forward to say he had been abused. It led to a flood of former members making similar allegations.

Police identified more than 80 victims, all under 16. Most were St John members.

The ring was headed by the man in charge of the Farnborough Division of the Brigade in Hampshire, Superintendent Leslie Gaines, 64.

Gaines, of Bognor Regis, West Sussex, admitted 11 charges of indecent assault. He also admitted five charges of buggery and one of attempted buggery. He was jailed for seven years.

Colin Hawyes, 51, of Farnborough, who succeeded Gaines as head of the division, was jailed for two years. He was found guilty after a trial on three charges of indecently assaulting boys.

The lodger at Gaines's flat, 69-year-old Eric Attfield, of Western Road, Aldershot, was jailed for seven years.

He was convicted of two indecent assaults, one offence of buggery and two attempted buggeries. He was cleared of one indecent assault and one buggery.

Cadets as young as nine

Mr Stewart Jones, QC, prosecuting, told Winchester Crown Court some of the cadets were as young as nine.

The victims had been sexually abused on camping trips and at Gaines's flat, which had been turned into a mini youth club.

Mr Jones told the jury that some of the offences were more than 30 years old - they all took place between the mid-1960s and the late 1980s.

Mr Jones quoted one former cadet abused by Gaines as saying: "These events deeply affected my life. I can't understand what they have done to me."

Another boy said: "The abuse I suffered has prevented me from forming stable relationships. It wrecked my education. I was expelled from school and got into trouble with the police."

Miss Susan Matthews, QC, told the court that Gaines was not a well man, suffering from angina. He had collapsed in the dock at one point.

She said he himself had suffered abuse as a child from a vicar. She added: "His whole life was to do with the St John Ambulance Brigade. And he did a tremendous amount of good for that organisation. But that has now been overshadowed by these events."

'Trust grievously betrayed'

Sentencing Gaines, Judge Patrick Hooton told him: "You were in a position of trust both towards the boys and their parents.

"They trusted you implicitly and that trust was grievously betrayed by you in the position of authority that you were."

After the case the Hampshire St John Ambulance Brigade said: "St John Ambulance expresses its sympathy to the victims and families involved in this case.

"We would like to assure the people of Hampshire and our 60,000 volunteers that the organisation is taking this matter very seriously.

"For the past 10 years St John Ambulance has been implementing a strict procedure to screen and monitor all new people and current volunteers."

Detective Inspector Peter Swan, who headed the investigation, said he was delighted with the convictions.

He said: "At one stage 25 detectives were working on the inquiry and we set up a full-scale incident room as you do in a murder case.