A radiant , HM Queen Elizabeth II of Britain accompanied by The Earl Mountbatten of Burma , went backstage at the Theatre Royal in London's Drury Lane at say Hullo to American musical comedy star , Mary Martin , who wore her stage costume from the show whose title role she plays , Hullo Dolly ! . The Queen met Mrs Martin after she had attended a Gala performance of the show , which aids the Historic Churches Preservation Trust . 7 December 1965