The Duchess of Cambridge joined her husband during the Wimbledon singles final on Saturday. Photographs obtained that day show the couple having a good time and laughing in the royal box.

       Body language expert Judi James explained what their demeanours suggest about their relationship.

       She said the royal couple’s gestures demonstrated the strength of their relationship and "raises it to a whole new level”.

       Ms James told Fabulous: "The shared joke is obvious here but it’s Kate’s 'overkill' response that suggests she is using the laughter to perform some industrial-strength flirt signals.

       "Kate’s response to William’s joke is to throw her head right back to laugh.

       “This exaggerated response of what looks like out of control laughter is a hugely flattering gesture to the person telling the joke."

       One of the photographs taken that day shows Prince William applauding the tennis players while his eyes are set on Kate.

       The expert explained: "His hands might be clapping the players but his eye-attention is fixed firmly on his wife here with his head turned fully in her direction and the angle of his shoulders signalling a desire for proximity.”

       Ms James previously explained how the Duke and the Duchess look like a “power couple” when attending engagements together.