The Mexican star reveals he was just 12 when he was tasked with pulling off his first lovemaking scene in a telenovela, and admits it was one of most embarrassing moments of his life.

Appearing on U.S. TV chat show Conan, Diego said, "When you go, 'When was the first time I had sex', you have to remember... I can just rent a film, basically!"

The young Luna was initially thrilled about the idea of getting intimate with the "amazing actress" he had a crush on and dreamed she would be so impressed with his manhood she'd want to date him offscreen - but then he turned up on the day of the shoot.

"I was very nervous," he recalls. "There's 40 people looking at me and I can just think of, 'Ah, I don't want to have a hard-on (erection). Please, please, please, I don't want to get too excited'.

"I was 12. I couldn't control it. She (actress) was very nice. She'd hide it (erection)."

And Diego's dream of impressing his co-star fell flat: "Obviously it didn't happen," he smiled.