Body language expert Judi James says there are interesting "power play signals" when Prince William hands Kate her new title.
James says Kate's body language is more military than regal, and that William responds to her look with a twisted smile.
This was William's first appearance at the parade since he inherited the title of Colonel of the Welsh Guards from his father.
Kate also handed out shamrocks to officers and warrant officers, a tradition that dates back to 1901.