The 40-year-old supermodel came face-to-face with the prince at a star-studded fundraiser the 31-year-old royal hosted on May 13 at Windsor Castle on Tuesday (13.05.14) and a TV crew caught their private conversation on camera.
Kate smiled at the prince and said: ''Where's your wife? She's not here?''
William then confirmed Duchess Catherine was absent from the event, to which the British beauty tilted her head to one side and gazed into the prince's eyes, before smiling and replying: ''Such a shame''.
Helena Bonham Carter also attended and recalled previously meeting the second-in-line to the throne when he was with Catherine on the island of Mustique before the pair wed in 2011.
After a few drinks, 'The King's Speech' actress managed to gain the confidence to ask whether he'd be godfather to her six-year-old daughter Nell - who she had with director Tim Burton - but he ''wisely'' refused.
She revealed: ''The duke and I met before, along with the duchess, before they were married, when I was staying on Mustique. I got very drunk at one point and I was determined to ask him to be a godfather to my daughter. He quite wisely said no.''
Take a look back at October's inaugural event.
The film is expected to continue without Mendes' involvement.