WENN

Rod Stewart had an awkward moment on his wife's U.K. TV talk show Loose Women on Friday when he was asked about cheating on her at the beginning of their romance.

The rocker was promoting his new album on the show when things got personal and Penny Lancaster's co-panelists asked him about his womanizing ways 20 years ago.

Rod, who wed Lancaster in 2007, had to watch footage of Penny talking about confronting her then-boyfriend after spotting him with another woman.

"He tried to tell me it was one his daughter's friends but I knew it wasn't and gave him an ultimatum there and then," Lancaster explained. "I told him, 'I don't want to be a girlfriend. I want to be the girlfriend'."

Red-faced Rod said, "She's had me under the thumb since then. There was just that one dalliance and we've been together ever since… I swore I was never going to get married again, but this one is irresistible."

Penny is Rod's third wife.

The couple also opened up about undergoing in vitro fertilization to conceive their youngest son, Aiden.

"We were just waiting for one (sperm) to go up and we said, 'Look at this one, it's swimming up there!," the proud dad explained. "We got that one sperm and that one sperm turned out to be our little son Aiden!"

Stewart is now a dad of eight with his kids ranging in age from 55-year-old Sarah Streeter, who was given up for adoption, to seven-year-old Aiden.