In a Radio Times interview, royal biographer Gyles Brandreth revealed some intimate details of Queen Elizabeth and Prince Philip's relationship, including why we've never spotted them holding hands.The two have been married for more than 68 years , and Brandreth chalks the strength of their relationship up to Philip's ability to make Elizabeth laugh, according to People . However, due to their generation's "stoic values," you probably won't see them showing much PDA. On top of that, Philip doesn't consider himself a romantic.But that doesn't mean they don't have a loving marriage. "If we regard the Queen's record-breaking reign as a success — and I think most of us do — Prince Philip is the co-author of that success," Brandreth explained. "The Queen wears the crown, but her husband wears the trousers. He is the power behind the throne — shrewd, steadfast, never-failingly supportive."Plus, they do engage in one romantic activity: singing together. "Her parents loved singing and passed it on," cousin Lady Elizabeth Anson said in BBC Radio Two's Our Queen: 90 Musical Years, according to People. "The Duke of Edinburgh and the rest of the family join in." Say it with me: D'aww.