Three former Barnet Council workers have been jailed for 35 years for historic sexual abuse.

Colwyn Baker, David Hennessy and Nigel Putman were all responsible for looking after vulnerable boys as residential care officers at Swaylands School in Penshurst, Kent.

The school was run by Barnet Council from 1968 to 1994, and the men were convicted last week of 28 counts of abuse dating back to the 1960s.

Appearing at Maidstone Crown Court yesterday, Baker, 71, of Craighouse Avenue, Edinburgh, was sentenced to 20 years in prison for 20 sexual offences, including two counts of buggery.

Hennessy, 74, of Westfields, in Narborough, Norfolk was sentenced to 12 years in prison for six sexual offences.

Putman, 62, of Kings Road, Slough, was sentenced to three years in prison for two sexual offences.

Last week, the jury returned 15 not guilty verdicts, and was unable to decide on a further five charges.

During the sentencing, Judge Statman said Baker had ruled by fear.

He added: “You must have thought as you entered your seventh decade that you had got away with it. But the extent of your criminality has been exposed.”

Judge Statman praised the victims for their “courage, dignity and restraint.”

He added that the investigation team, made up of more than 30 officers, had shown extraordinary compassion and sensitivity and said they should receive commendations for their work.

Judge Statman said: “In my judgement I have seen in this courtroom policing of the highest standard”.

After the first victims came forward in 2011, officers reviewed old school registers and visited potential victims or witnesses in person to ask if they wanted to help with the investigation.

In all, 65 former pupils made allegations, and the three defendants were eventually charged with 48 counts of sexual abuse against 24 children.

Detective Superintendent Paul Fotheringham of the Kent and Essex Serious Crime Directorate said: “This sentencing brings to a close a comprehensive investigation that has lasted a number of years. I’m pleased with the sentences that have been passed, and it shows that no matter how long the passage of time, if you are convicted of carrying out sexual offences you will feel the full weight of the law.”

Det Supt Fotheringham said some children who tried to resist abuse were beaten or refused food, and their classmates would be denied leisure activities to make the victim unpopular or feel guilty.

He added: “Despite the weight of this corroborative evidence, the three men refused to admit to their crimes. Instead they forced their victims to appear at court and recount the abuse they had suffered all those years ago.

“All the victims were involved in the process and have been kept fully up to date. This is justice for all of them and I’d personally like to thank all those who have helped bring this case to a conclusion.”

Swaylands School, near Tonbridge, was closed in 1994. Initially it was for boys with moderate learning difficulties, but from 1987 was redesigned to accommodate boys with emotional behavioural difficulties.

Pupils were placed there from across London and the south east.

Hennessy and Baker had previously been convicted of similar offences committed at the school. In 1993, Hennessy was convicted of four indecent assaults and two offences of buggery on one boy.

In 1994, Baker was convicted of four indecent assaults and one gross indecency, against three boys.

Both men were sentenced to three years for each offence, to run concurrently.

In light of that initial investigation and the fresh allegations, Barnet Council commissioned a report from the Lucy Faithful Foundation.

Pete Saunders, founder and spokesman of the National Association for People Abused in Childhood, said: “NAPAC applauds the fantastic work that Detective Superintendent Fotheringham and his team has achieved in bringing these child abusers to justice.

“We are pleased to have worked alongside them in this difficult and sensitive work, and are most encouraged by Kent Police’s caring attitude and behaviour towards the victims of these vile crimes.

“This case should act as a benchmark for police forces nationally on how to handle this type of investigation.”

The offenders were also required to register as sex offenders and will be the subject of sexual harm prevention orders.

In a statement last week, a Barnet Council spokesman said: “No child should have their life scarred by sexual abuse and today's verdicts underline the importance of making sure that historic child abuse allegations are properly investigated and prosecutions brought, no matter how long ago the abuse took place.

"Everyone at this council is truly sorry that young boys suffered in this way."