The Princess of Wales appears to be sending a secret message to Prince William with a "deliberate" move in new picture to mark her 43rd birthday.

A previously-unseen picture of the royal - who turned 43 yesterday - was released alongside William's sweet message to his "incredible" wife. The new picture is said to have been taken last summer by photographer Matt Porteous.

Celebrating his wife, William's message read: "To the most incredible wife and mother. The strength you’ve shown over the last year has been remarkable.

"George, Charlotte, Louis and I are so proud of you. Happy Birthday, Catherine. We love you. W."

In the black-and-white picture, Kate is seen sporting a casual look of jeans, a shirt and a blazer. Also wearing a check scarf, the royal is seen with her hands in her pockets - but making sure not to hide her £390,000 engagement ring.

Discussing the ring, body language expert Darren Stanton shares that this is a subtle nod to "her rock" William.

Speaking on behalf of JeffBet, he said: "Her choice of clothing is understated yet stylish. She’s wearing tailoring in the form of a blazer, but it’s open and the collar of her blouse is unbuttoned. She’s wearing jeans too and her hair is styled but flowing freely.

"The only piece of jewellery she has chosen to wear is her engagement ring, and despite her hands in her pocket, it’s fully on display."

He added: This signals to me that she’s paying tribute to William and their marriage. She didn’t want any other piece of jewellery to distract and she wanted to let the ring take centre stage.

"It’s a very deliberate move. They’ve been through a challenging year and William has no doubt been her rock."

Kate's birthday is not usually marked by a message from William - or the release of a new image.

It is, however, understood that William wanted to mark the occasion following Kate's "brutal" year receiving cancer treatment.