Allison Janney decided not to introduce herself to Prince William and Duchess Catherine at the BAFTAs - in case she broke royal protocol.
The 58-year-old actress won the Supporting Actress gong for her role in 'I, Tonya' at the prestigious ceremony at London's Royal Albert Hall on Sunday (19.02.18), and was overcome with "joy and emotion" when she saw the royal couple in the front row when she collected her prize.
However, she opted to just "smile and stare" rather than speak to them just in case she said something "wrong".
Speaking to reporters on the red carpet, Janney said: "I got hit by a wave of joy and emotion. It was extraordinary. Then having Kate and William right there in the front row.
"I was just looking at them. I couldn't even ... I didn't know whether I would say hello or anything to them.
"And then I looked at them and thought, 'No! You're going to say something wrong. You don't say Kate and William. You say Regina.'
"So whatever. I decided to just look at them, smile and just stare."
Duchess Catherine, 36, didn't wear all-black to the BAFTAs in support of the anti-harassment Time's Up campaign, but the 'Tammy' star, who did, said no-one has the right to discuss another person's clothing choice, and added that she was "so happy" the couple - who have four-year-old Prince George and two-year-old Princess Charlotte - are expecting another child.
She said: "I would never judge anyone's choice of what they're wearing. She looked absolutely beautiful, and I'm so happy for them and that she's pregnant again."