By Graeme Murray A personal gift to King Charles from Prince Louis gave the monarch a real ‘spring in his step’, a royal commentator has claimed. When he returned to public duty on Tuesday, the 75-year-old quietly let royal fans know he was wearing a pink dinosaur tie which was said to be a gift from one of his grandchildren. He wore the colourful T-rex tie when he visited a cancer treatment centre in London. Commentators believe it was a present from six-year-old Prince Louis, six, who is said to have a penchant for dinosaurs. Royal expert Robert Hardman told the MailOnline: “His tie said it …