The Prince and Princess of Wales carry out lots of public engagements but they also hold private meetings, which are recorded in the Court Circular.
Prince William and Kate met with Apple's CEO Timothy Cook at Windsor Castle on Thursday afternoon, with Mr Cook later sharing images from their one-to-one.
"It was a true honor to meet with the Prince and Princess of Wales. We had a wonderful and wide-ranging discussion about the environment, mental health, and other issues that mean a great deal to all of us," he wrote in a tweet.
The snaps show Mr Cook with the royal couples in one of the Castle's opulant rooms, with William dressed in a navy suit with a pale blue shirt, while Kate donned a business-casual look with a pin-striped pant suit from Holland Cooper and a camel roll neck.
In the photo of Mr Cook and the Prince together, bags with the Apple logo can be seen on the coffee table in the background.
However, protocol dictates that members of the royal family cannot accept formal gifts.
The gift policy, which is available to read in the royal family's official website, states that "no gifts, including hospitality or services, should be accepted which would, or might appear to, place the Member of The Royal Family under any obligation to the donor".
William previously teamed up with Apple Fitness+ to record an episode of Time to Walk in December 2021.
As the Prince led listeners on a tour of the Sandringham estate in Norfolk, he spoke about the importance of keeping mentally fit and shared a few personal anecdotes.
In one light-hearted moment, he revealed how he was taken out of his "comfort zone" during a charity fundraiser in 2013, when he joined Jon Bon Jovi and Taylor Swift on stage to sing Livin' On A Prayer.
William said about the experience: "Beneath my black tie, there was a lot of sweating going on. I felt like a swan, where I was trying to keep myself composed on the outside, but inside, the little legs are paddling fast."
© GettyHe added: "Now, a lot of people might think that I’m comfortable on stage. When I do speeches and things like that, I’ve done so many now, they’re not a problem. But I’ve not done singing. At times, when you’re taken out of your comfort zone, you’ve got to roll with it.
"And I think we’ve gotten to the stage in this life where we do micromanage ourselves. We do worry about: how do we look on social media? Who said what about me? What am I wearing? There’s so many pressures, but I think making a fool of yourself is okay."
The meeting with Mr Cook also came the day before William's visit to Swindon based charity BEST – Be A Better You to hear about the work it does to provide young people with mental health support through sports coaching.
Earlier this week, the Princess of Wales visited textile manufacturers in Leeds and Lancaster, where she learned more about her family connections to the industry.
On Wednesday, Kate was in Kent to join a fun-filled sensory session with children, who have specialist educational needs and disabilities, to highlight the important work of the National Portage Association.
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