Peter McCormick, 66, engaged in lewd, indecent and libidinous practices towards the youngsters between 1978 and 1997.

Police Scotland said the boys were under the age of 13 at the time they were preyed upon.

The Crown Office and Procurator Fiscal Service (COPFS) said the first victim had gone with friends to McCormick's home in Stirling in 1978, where they were given cannabis and alcohol by the then 20-year-old.

After falling asleep on the offender's bed, the boy woke up to find McCormick abusing him.

COPFS said McCormick gave his second victim cigarettes and alcohol during a sleepover at his home in the summer of 1978.

That boy also woke up to find McCormick sexually abusing him.

The following year, McCormick supplied his third victim with alcohol and encouraged him to keep drinking.

He too woke up in the middle of the night to find McCormick abusing him.

Prosecutors said McCormick preyed upon his fourth victim between 1994 and 1997.

The boy recalled McCormick being nice to him and buying him sweets.

McCormick then began asking the youngster questions of a sexual nature and showing him pornography before going on to sexually abuse him.

Scotland's Crown Office said the sexual abuse took place at McCormick's home and at various other locations for two years.

Katrina Parkes, Scotland's procurator fiscal for high court sexual offences, said: "Peter McCormick manipulated and exploited these young children in an abhorrent campaign of abuse.

"His victims have shown great courage and strength by coming forward and reporting him to the authorities.

"McCormick will now have to face the consequences of his actions."

McCormick pleaded guilty to four charges at the High Court in Glasgow in May. He returned for sentencing on Monday.

As well as the five-year jail term, he was also placed on the sex offenders' register indefinitely.

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Detective Constable Ian Philip, of the Forth Valley Public Protection Unit, urged anyone who has been impacted by this type of crime to report it.

He added: "This was a complex and disturbing case and it is right that McCormick now has to face the consequences of his disgraceful actions.

"My thoughts remain with the victims and their families. This conviction is a direct result of them coming forward.

"They have shown immense courage in reporting these crimes so that McCormick can been held accountable for his actions.

"I hope that his conviction gives them some comfort and they can try and move forward with their lives."