John Torode and Gregg Wallace are "not as friendly off screen" and have never been to each other's houses.
John Torode and Gregg Wallace
The 'MasterChef' judges - who have appeared on the BBC cooking show since 2005 - have a "calm" relationship, but John revealed the pals have "never really cooked for each other".
He joked: "I had to wait until his fourth wedding before I got invited to be his best man.
"It's well documented that we don't socialise outside of work.
"We've never been to each other's houses. We've never really cooked for each other.
"We spend a lot of time together, sharing a lot of things: emotion, food, pressure and changing people's lives. And 17 years on, it's still a relationship that is calm and in good stead. I think it's an amazing thing."
Gregg also admitted there is "no ego clash" between the pair, and they don't fight for screen time on the programme.
He said: "We trust each other completely. We feel safe with each other. We know that the other one isn't going to - on camera, anyway - ridicule the other one.
"We don't fight for space. We don't fight for time. There is no ego clash.
"People are really interested in my relationship with John. I think because we're so friendly on screen, they find it really difficult to understand why we're not as friendly off screen."
But Gregg admitted it has become "a bit of a ritual" for the pair to enjoy lunch together when they are away on location overseas.
Speaking to the Radio Times magazine, he added: "It's just me and him. We buy a nice bottle of wine and we can chat about anything."