Former News of the World royal editor Clive Goodman hacked Kate Middleton's phone 155 times and Prince William's mobile on 35 occasions, the Old Bailey heard.
The voicemail of Kate Middleton -as she then was- was hacked on Christmas Eve, Christmas Day, and Boxing Day in 2005.
Clive Goodman said he had hacked her phone 155 times in nine months - and only stopped the day before he was arrested.
He also owned up to hacking the phones of Prince William and Prince Harry.
ITV News Correspondent Juliet Bremner reports: