The Duke and Duchess of Cambridge are a complete power couple. It would be hard to deny this marriage. [Prince William and Kate Middleton basically had the exact same expression on their faces at every turn while watching a tennis match, proving their strong bond tenfold.

But don't take it from me: body language expert Darren Stanton observed how bonded the Cambridges seemed during the event.

"If you're an avid tennis fan, it's obvious that both Kate and William are engaged in the on-court action while watching the match on center court," Stanton told Marie Claire on behalf of Slingo (opens in new tab).

"In a tense moment on the court, Kate anxiously tucked her hair behind her ear and William looked nervous.

"At times, Kate could be seen with a big, happy smile on her face. Her smile was sincere and her whole face was drawn as if she was soaking in the atmosphere."

For Stanton, this appearance was a powerful foreshadowing of what could be expected of William as king.

"As always, an outing on such a public scale," he says, "would see Kate and William setting the precedent and the scene for how things should be for when William becomes king.

"The two are not afraid to be themselves, while also following their royal duties with grace and as much integrity as possible.