The two actors appeared opposite one another in the long-running sitcom As Time Goes By, in which they played a former couple who reunited after 38 years apart.
As Time Goes By ran for nine series between 1992 and 2005, but in a new interview with Radio Times, Dame Judi admitted that she and Geoffrey – who died earlier this month, aged 93 – had a bit of an awkward moment during their first meeting.
She told the magazine: “We met for lunch to discuss the show, he got us off to a good start when he informed me that they’d wanted Jean Simmons for the part, but she’d declined!”
Despite their shaky start, Dame Judi became firm friends with her co-star, who she says was a “remarkable actor”.
“He’s unsurpassed as far as comedy is concerned, aided by that lugubrious face and his amazing voice,” she said.
Dame Judi previously paid her respects to Geoffrey earlier this month, revealing he was frequently getting her into trouble on the set of As Time Goes By.
“Oh my goodness how we laughed,” she said. “There were a lot of outtakes. He got me into endless trouble.
“I have admired him all my life. How lucky to have been in something with him for so long.”
Radio Times also featured a tribute from Geoffrey’s Butterflies co-star Wendy Craig, who said: “Geoffrey was a cool actor – he didn’t push it. Everything was understated. He had a great sense of comedy and I’ve never met an actor with a better sense of timing.
“The most beautiful thing was his voice. It was unmistakable, with its smooth, seductive, perfect diction. It’s no wonder he was used on those car commercials.”
In addition to As Time Goes By, Dame Judi and Geoffrey both appeared in the James Bond film Tomorrow Never Dies, in which he played Admiral Roebuck, and she reprised her role as M.
Read more in the new issue of Radio Times, on sale now.