The Queen star reveals she hated the sight of the clunky footwear when she first saw a friend sporting a pair during the New Orleans Jazz Fest in Louisiana, and she was even more shocked when she spotted her "stylish" friend Cumming donning the shoes backstage at his Broadway show Cabaret.

She explains to U.S. talk show host Jimmy Fallon, "The first time (I saw Crocs) was in New Orleans and my friend wore them in the mud of Jazz Fest and I went, 'Those are the most hideous shoes I have ever seen in my life. How can you be seen in those shoes?' And my friend said, 'Well, they're good in the mud.'

"And then I see Alan, and Alan is a very stylish guy, really cool, sharp dresser and he's wearing these hideous things on his feet! I said, 'Alan, how can you be seen dead in those shoes? They're so awful. It's the second time I've seen them. I can't, they're just the most ugly things I've ever seen.'"

However, Mirren had an unexpected change of heart when Cumming convinced her to try on the Crocs for herself.

She continues, "He said, 'Try a pair on, you'll see.' So I found a pair, I tried them on and I'm a complete addict now. I wear Crocs all the time! They're fantastic, but also, you can wash them in the dishwasher! I wash mine in the dishwasher. Why not? Not with the dishes!"

The Oscar winner now has another pair to add to her collection after receiving a white set of Crocs with the Union Jack flag painted on the front from The Tonight Show Starring Jimmy Fallon presenter. She even kicked off her high heels on the show, which aired in the U.S. on Monday night (30Mar15), to don her new favourite shoes.