A high court judge granted the MasterChef presenter, who is currently dating actress Lisa Faulkner, an uncontested decree nisi in less than a minute.
John and Jessica, who have an eight-year-old son and a seven-year-old daughter together, mutually agreed to separate in 2011 after seven years of marriage.
The following year Melbourne-born John, 48, and 41-year-old Spooks actress Lisa went public with their romance.
John with Jessica in 2010
The couple first met when Lisa stormed to victory in 2010's edition of Celebrity MasterChef.
"John and I were friends," Jessica told the Daily Mail in 2013. "Neither of us thought of it as anything else until... I don't know how things change, but something does.
"He asked me on a date. We went out for dinner. Then it was slightly different," she added. "I'm really, really happy. John and I are having such a nice time but we're taking things slowly. There are lots of other people to consider."
John and girlfriend Lisa in 2011
'When I met John he was a judge on a show I loved and I was petrified of him," she said. "He was brilliant and gave us all tips so you didn't want to let him down
"John and I always got on, but I never thought about me and him."
Shortly after John and Jessica went their separate ways, Lisa divorced her husband, EastEnders actor Chris Hoghill, and he moved out of the London home they shared.
Lisa and her adopted daughter Billie
Chris and Lisa, who has released two recipe books since her triumph on MasterChef, have joint custody of their six-year-old adopted daughter, Billie.
John has four children, two with Jessica and two from a previous relationship.