A former cub scout leader dubbed a “paedophile hiding in plain sight” has been jailed for sexually assaulting boys as young as seven since the 1990s.

Ian Silvester, of Locks Hill in Portslade, East Sussex, had befriended his victims working as a babysitter, diving instructor, first aid trainer and St John Ambulance trainer.

He had previously denied 83 charges of historical sexual abuse in Hove and Worthing, but was found guilty of 79 of those charges following a trial at Lewes Crown Court in November.

Silvester, 60, was sentenced to 16 years in prison with an additional six years on licence at the same court on Friday.

Sentencing Silvester, Judge Christine Laing KC said: “You are the very definition of a paedophile hiding in plain sight.”

The judge said the defendant had given his victims a “lifetime of shame and regret”, telling the court the abuse happened so “openly and plainly and so often in front of others”.

She added: “The fact is, you were in a position of trust with each boy.

“Either as their babysitter, their cub scout master, their diving coach, a provider of first aid training, claiming to meet them to practice to be victims, and your behaviour was a gross abuse of that trust.”

An impact statement read out in court from one man who was abused by Silvester said: “You are a monster who picked the most vulnerable in society.”

On devices seized from Silvester’s home were images and videos of his victims being assaulted by him as well as indecent images of children, online chat logs and web searches of sexual interest in young boys.

Silvester was found guilty of 44 counts of indecent assault on a male, 25 counts of sexual activity with a child, four counts of sexual assault, two counts of inciting a child to engage in sexual activity, two counts of sexual assault of a child under 13 and two counts of making indecent photos of children.

Sussex Police investigator Nicky Beard said: “For over three decades, Ian Silvester abused the trust placed in him by his victims and their parents, in the most appalling ways.

“He was relentless in seeking and creating roles which allowed him continued access to boys and young men, many of whom were vulnerable, and he would ruthlessly abuse them for his own sexual gratification.”

A spokesperson for the Scouts Association said Silvester would “never again be allowed to volunteer with the Scout Movement”.

It added: “There is no place in the organisation for anyone who behaves in this way.”