It might have been just another day for Richard Harper, a young IT engineer, as he sat down to mend a computer in his workshop in Reading. As he ran tests he came across a folder marked “young boys” on a hard drive slotted into the back of the machine. He clicked on an icon. What he found stopped him in his tracks: a shocking image of a child. Appalled, he called his manager.

That was the moment in August 2007 when one of the most brutal criminal conspiracies in recent Scottish legal history began to unravel. Over the next ten months, eight serial child-abusers would be picked up by the police, as their casual internet chats and brutal photographic exchanges revealed lives of lurid fantasy and the all-too-real abuse of children and babies.

Exposing the conspiracy was to involve an extraordinary international operation, based at police headquarters at Fettes in Edinburgh, which drew in the skills of Scottish and American academics, FBI agents and Microsoft personnel in San Jose, California, revealing on its way a paedophile network that extended all around the world.

But it might never have succeeded had it not been for a single act of forgetfulness by Neil Strachan, when he sent his computer to be repaired.

Only ten days after the hard drive arrived at Edinburgh police headquarters Strachan was arrested.

His world of e-mail aliases, international contacts and grotesque images would be painstakingly revealed.

One of Strachan’s main correspondents was James Rennie, 38, a gay rights campaigner who had managed the Stonewall Youth Project before his appointment as chief executive of LGBT Youth Scotland, an organisation which campaigns for the rights of lesbian, gay, bisexual and transgendered young people. Rennie was an opinion former, a mover and shaker.

He was consulted by the Scottish Parliament over youth policy. He met the Queen and went to Downing Street to shake hands with Tony Blair.

Police also uncovered links with Matthew Grasso, a notorious sex offender in Salem, Massachusetts, who was indicted in 2007 for having 150,000 images of child abuse in his home. Rennie had further connections to 300 child abusers in the United States, Australia, Germany, the Netherlands and Poland, many of whom are still being pursued.

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