The pair interviewed each other for the magazine, and talk about their first encounter and bonding over a shared love of tequila.
"We met at an event at Windsor Castle, but only really briefly," recalled Margot. "I know this sounds like I just rub shoulders with royals all the time, but Prince William was at the event. It was that kind of thing, a super-fancy event.
"I remember muttering to my friend Sophia [Kerr], when this waitress asked, 'Would you like water? Would you like champagne?' I said, 'God, I want a tequila.'
"Cara, who I’d never met before, was about five metres away from me and her ears just pricked up and she said, 'Did someone say tequila?'
"I was like, 'You and I are so going to be best friends.'"