Prince William, 41, hosted an investiture at Windsor Castle before attending a fundraiser gala for London's Air Ambulance Charity on Wednesday.
Arriving at the dinner, the father-of-three waved to people gathered outside the venue in London.
He said: "We really appreciate everyone’s kind messages, thank you."
Noor Hibbert, Celebrity Mindset Coach and Body Language Expert, tells HELLO! that William naturally put on his "game face" as he arrived at the star-studded bash.
"Observing Prince William's arrival as he got out of the car, he takes a few moments to adjust his trousers and his shirt. Whilst this may seem a logical thing to do when getting out of the car, it's also an unconscious cue to the mind to put on his game face."
Noor continues: "Whilst his personal life may seem in turmoil with the worry of his father's cancer, Kate's recovery amongst other things, he's now in the public eye. Therefore, by making subtle adjustments to his outer physical appearance, he signalled a shift in his demeanour and his energy as he was ready to slip out of husband/son mode and into a Prince in the public eye mode."
William later delivered a pre-dinner speech to the audience, saying: "I'd like to take this opportunity to say thank you, also, for the kind messages of support for Catherine and for my father, especially in recent days. It means a great deal to us all. It's fair to say the past few weeks have had a rather medical focus, so I thought I’d come to an air ambulance function to get away from it all."
Noor observes: "As he gets up to make his speech, he seems to be lacking some confidence, which can be a by-product of somebody who has a lot on their mind. His head is ever so slightly tilted with his eyes facing downwards and it takes a good few moments before looking up at the audience to acknowledge them.
"This gesture can mean several different things. I would expect it was a mix of him, preparing and getting focused on simultaneously, a slight level of unconscious discomfort and avoidance when someone is feeling particularly vulnerable or exposed. This can provide subconscious respite from the vulnerability as he is most probably feeling drained with emotion with the current situation."
Noor adds: "He also coughs to clear his throat before addressing the audience. Doing one cough can often be a nervous tic or habitual behaviour triggered by stress for anxiety - which would be understandable, given his circumstances. It can also serve as an unconscious way of releasing some of that tension.
"William may be the Prince in the public eye but firstly he is a son and husband and no doubt all of the experiences of the last two weeks will be weighing heavy upon him emotionally."