Gary Campbell, 59, from a remote village in Sutherland, was traced by cybercrime investigators through online payments he made to foreign accounts.

In what is believed to be a legal first in Scotland, prosecutors from the Crown Office and Procurator Fiscal Service (COPFS) were able to prove Campbell’s direct involvement in the rape and sexual assault of girls thousands of miles away.

The former retained firefighter – who also worked for Scottish Water – admitted sexual abuse charges involving children as young as four. No child was older than 13.

The Crown proved that Campbell was personally involved in the abuse and just as responsible for the attacks as his fellow perpetrators in the Philippines, known in law as “art and part” guilt.

He was convicted under legislation protecting children anywhere in the world from sexual abuse by British nationals.

He was tracked to his home in Scotland after an international investigation into the live-streaming of child sex assaults by abusers in the Philippines.

Over Skype, Campbell initiated serious sexual assaults and rape, demanded that the victims be very young, negotiated online payments and issued explicit instructions as children were assaulted.

All of this was conducted in real-time, through live communications, and recorded on devices later recovered from Campbell’s Highlands home.

Campbell, who has since moved to Perth, pled guilty to 13 charges at the High Court in Edinburgh last month.

He was sentenced to 12 years’ imprisonment and was given a three-year sentence extension, during which he will be subject to close supervision.

His name was added to the sex offenders register indefinitely.

Fraser Gibson, Scotland’s procurator fiscal for High Court Sexual Offences, said Campbell was complicit and instrumental in appalling crimes against children.

He added: “Gary Campbell was actively involved in a paedophile network in which children were abused for money and on-request.

“The girls assaulted and raped in the Philippines were vulnerable young children suffering dreadful abuse and exploitation.”

“British nationals who sexually abuse children abroad will face justice here. Legislation allows us to prosecute them and we will use every power available to us to ensure that they do, working with specialist police, international partners and cybercrime teams to track down these abusers.

“I would urge anyone with information or knowledge of this kind of offending to come forward and report it as soon as they can.”