A former Church of England Boys' Society lay leader and scripture teacher at Sutherland has been sentenced to a minimum three years and seven months jail for historical child sexual assault offences.

Many of the offences occurred in church-run camps for boys in Royal National Park.

William Richmond Sandwell, 78, of Loftus, appeared in the District Court, Downing Centre, after a jury found him guilty of 11 child sexual assault offences, committed against six children between 1965 and 1985.

Sandwell, who also used the name Sandell at one time, denied the offences.

Among "survivors" in court for the sentencing was Alexander Hayes, who now lives in Perth.

Mr Hayes said outside the court Sandwell's assaults on him between the ages of 11 and 15 had had a "catastrophic effect on my life and a horrific impact on many families, including his own."

"It hasn't stopped me leading a good life, but it has had a big effect on me socially," he said.

"I have been married and divorced three times, and its affected the intimacy I have with other people."

Mr Hayes said he believed Sandwell would have assaulted many more children over 30 years and that the church was aware of his actions from as early as 1991 and covered it up.

Sutherland police charged Sandwell in 2017 after investigating allegations of sexual assault of boys, who were members of the Church of England Boys' Society (CEBS).

Judge David Arnott said Sandwell was a senior lay member of St John's Church, Sutherland, and, through this involvement, was also a leader of the parish's CEBS branch.

CEBS ran weekly Friday night meetings where the boys played games, and there was also a big focus on camping trips.

The judge said Sandwell's offences ranged from fondling the genitals of boys to one instance of digital penetration, which was "particularly callous".

Six offences had been against one boy.

The judge said, on one occasion, Sandwell told the boy he could not attend a camp sailing regatta because he had done something wrong.

Sandwell had then ordered him to take a shower.

The boy had panicked in the shower and tried to push past Sandwell, but the offender had prevented him leaving and then assaulted him.

The judge said another boy testified he had "frozen in shock" when he was assaulted while lying in a sleeping bag.

The judge said Sandwell was also a primary school scripture teacher and, on a weekend camp, assaulted a boy aged 11-12.

This boy, in his victim impact statement, had said he "changed from being a typical well behaved child to a self-destructive lifestyle".

The court heard Sandwell was a father of two, grandfather and great grandfather.

He was married for 54 years and his wife died in 2016.

The judge said Sandwell was raised by his mother and grandparents and only had contact with his father on two occasions.

In imposing sentence, Judge Arnott said he had taken into account a range of factors, including Sandwell's age, poor health and the fact he had not shown remorse.

He sentenced Sandwell to a non-parole term of three years and seven months, backdated to when he was convicted and refused bail in March this year.

An additional term of two years and five months can be applied if he does not meet parole conditions.