A FATHER-OF-TWO who groomed young girls for sex over the internet has been given a life sentence following a police investigation that spanned the globe.

Gordon McDonald, 57, of Penicuik, Midlothian, will serve at least four years behind bars before being able to apply for parole.

Judge Lady Stacey told McDonald at the High Court in Glasgow: "I regard you as a danger to young girls. It will be up to the parole board when, if ever, you are released."

Solicitor advocate Matthew Auchincloss, defending, told the High Court in Glasgow McDonald was a law-abiding family man until he became obsessed by porn and internet chat rooms.

He added: "We are allowing strangers into our children's bedrooms through the internet.

"Mr McDonald first looked at adult porn then descended into indecent pictures of children and contacted young girls. He says it was out of control and only came to an end with the police knocking on his door."

McDonald groomed one 13-year-old girl on the internet and got her to meet him after school. He drove her to a deserted industrial estate where they stripped naked and performed indecent acts on each other, including the use of sex toys.

Eventually the girl told a teacher what had been happening and police began a major investigation.

McDonald pled guilty to a total of 13 charges, which took place while he lived in Cumbernauld, North Lanarkshire, between November 2005 and March 2011.

The married maintenance engineer admitted indecency and meeting or arranging to meet girls under 16 for sex and possessing child pornography.

Advocate depute Jane Farquharson, prosecuting, told how McDonald used a series of aliases when logging on to teenage chat rooms or communicating one-to-one with girls using the MSN link. At different times he posed as a teenage boy, a young girl who was curious about sex and a transvestite.

In other conversations it was obvious he was an older man and, describing to one girl how he would like to have sex, he kept calling himself "Daddy".

The court heard the sexually explicit internet chats with McDonald involved 10 girls aged between 12 and 15.

Their identities were revealed when police raided McDonald's home and seized computer equipment and a camera.

A total of 4432 indecent images, both stills and video clips, were recovered.

Following sentencing yesterday, Strathclyde Police said victims of McDonald's online sexual offending were located at various addresses across the UK and overseas.

The investigation involved officers from the Metropolitan Police Service, West Mercia Police, Nottinghamshire Police and Avon and Somerset Constabulary.

Detective Chief Inspector John Weir, of Strathclyde Police Public Protection Unit, praised the courage of his victims, many of whom had never spoken before about their ordeal.

He said: "Today marks the end of an intense, sensitive and complex investigation.

"Our thoughts remain with the victims and their families but I hope today's sentencing can bring some solace to them in the knowledge the person responsible has been held to account for his actions and those victims can now move forward with their lives.

"This has clearly been an incredibly difficult time for the victims and their families and I would like to take this opportunity to pay tribute to them for their courage and determination in coming forward and speaking to us.

"There is no doubt in my mind their testimonies proved vital in helping to ensure Gordon  McDonald was arrested by police and prevented from preying on other children."