Sir Ron Brierley pleads guilty to three counts of possessing child abuse material
Brierley, 83, accused of having 207,000 images and videos of kids as young as 2
He was arrested in December 2019 after a tip-off to police months earlier
The New Zealand-born Brierley was once a feared international corporate raider
Jacinda Ardern has called for Brierley to be stripped of his knighthood