The Prince of Wales made a key gesture during the Princess of Wales's Christmas carol concert on Friday which showed "reassurance", according to a body language expert.

Princess Kate attended her annual Together at Christmas Carol service at Westminster Abbey as she makes a gradual return to public events after completing her cancer treatment.

It marked a milestone for the future Queen who spoke about "challenging times" and about how she "didn't know" what this year would bring during her last Christmas carol concert.

Kate arrived at the abbey ahead of the service to greet and speak to her guests before she was joined by Prince William and their three children, Prince George, Princess Charlotte and Prince Louis and the rest of the royals.

According to body language expert Darren Stanton, there was one poignant moment ahead of the service, which showed a "non-verbal reassurance gesture" by the future King.

Speaking on behalf of Slingo, Mr Stanton said: "Kate is taking the lead. We see William walk up to Kate. He puts his arm on her elbow, a nonverbal reassurance gesture. It was a really nice touch."

He also noted the princess's decision to stand at the rear when moving with her family, a 'protective' and 'dominant' gesture, which showcased how strong the couples' bond is.

Mr Stanton explained: "When they're moving together, she stands at the rear. That’s a protective, dominant gesture; the leader stands at the back.

"She’s very nursing and protective. I think if anything, this year has reinforced how strong they are and how much they are in love with each other.

"William has not seemed himself when Kate is not there. The interactions between the two of them indicate a much deeper connection."

He added that the princess showed she was "confident" but "tired" as she appeared at her annual carol concert.

He explained that she showed "no signs of nerves" and praised her for "working hard" to make sure she is "up to speed" after spending most of the year out of action, with "genuine" and "authentic" smiles on display.