During the interview, at his farm in Devon southwest England, he did detail the couple’s affair which was a world away from royal life.
“Well, I’d cook and she’d wash up. Just dinner and relaxing and laughing,” he said.
The couple were forced apart when Hewitt, an officer in the British Army, was deployed to serve in the Gulf War, before the affair was later exposed to the media.
It is believed that her husband Prince Charles, was at the same time having an affair with his now-wife, Camilla parker Bowles.
Asked if he regrets meeting the princess, he replied, "No, I don’t regret that.".
"I regret some of the things that have been caused by that but not that at all. No way," he said. "I think she was quite easy to fall in love with really so I think I can be forgiven for that."
As well as her affair with Hewitt, the special, which commemorated 20 years since her tragic death, also interviewed Diana’s bodyguard Ken Wharfe, best friend Rosa Monckton as well as butler Paul Burrell.
Burrell claimed he had a letter from Diana written months before her death, in which he says predicted her own death.
“This particular phase in my life is the most dangerous," he read out in the letter. "My husband is planning ‘an accident’ in my car, brake failure and serious head injury in order to make the path clear for him to marry Camilla.”