An Australian investment banker has pleaded guilty in the “collar bomb” extortion scheme that caused worldwide notoriety last year.

Paul Douglas Peters appeared in a Sydney courtroom on a video screen from prison as his lawyer entered the plea on a charge of aggravated breaking and entering.

Bill Pulver, the father of Peters' teenaged victim, expressed satisfaction his daughter Madeleine will not have to go through a grueling trial, where she would have been the star witness.

“We are incredibly pleased with today's outcome. It is great comfort knowing that Maddie will not have to endure the stress and anxiety of reliving the events of that terrible night. Today's guilty plea brings closure to a crime that remains a mystery and random to us in our mind as it did back on August the 3rd.”

Peters broke into the Pulvers' Sydney mansion in August wielding a baseball bat and found 18-year-old Madeleine alone in her bedroom, where she was studying. He chained a device he said was a bomb around her neck and left behind a note demanding money.

Pulver wore the device for 10 hours before police were able to remove it and determine it was fake.

Peters fled to the United States, where he was arrested two weeks later at his former wife's home in Louisville, Kentucky. He was extradited to Australia in September.