Speaking at the Britain's Got Talent press launch yesterday, David joked that he was a bit in love with Simon.
"Lara's jealous, because every time I come home from work I say, 'Oh, guess what Simon did today, guess what Simon said. She actually doesn't really like it," he jokingly said.
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But David couldn't resist getting a few more laughs, as he went on to say: "And also, in our wedding photographs I've taken her head away and stuck Simon's on top."
As we started giggling, David continued: "And sometimes, when we get into bed at night, I ask if it's OK if I call her Simon. The first few times she didn't mind. But then she's wearing the mask..."
Simon Cowell then interjected, comparing David with his pet dog. "It's been a very entertaining relationship," he said.
"My mum and dad used to have a dog and as it got a bit older, it used to get on my leg occasionally and hump it. In the end, you're like, 'Oh Lottie, just go away. That's kind of our relationship."
He continued: "You know the sketch he does on Little Britain with the Prime Minister and the gay assistant? That's our relationship."
David couldn't resist butting in: "Except you're the gay assistant!"