The Crown, which has a reported budget of $160 million (£100 million), will chart the Queen's life from her marriage to Philip, Duke of Edinburgh in 1947 to the present day.The script for the 20-hour epic will be penned by Peter Morgan, the screenwriter behind 2006 film The Queen, with the assistance of director Stephen Daldry.Casting officials are said to be looking for three actresses to play the monarch in different stages of her life.A source tells the Daily Mail: "There will be hundreds and hundreds of roles to be cast, from prime ministers to international leaders such as the U.S. presidents she has met. And probably Nelson Mandela will be in there, too."And don't forget Prince Philip - that's going to be a huge role for an actor, or more likely several. People will play Charles (Prince of Wales), Diana (Princess of Wales), Camilla (Duchess of Cornwall), William (Prince William), Kate (Catherine, Duchess of Cambridge)... the whole lot of them."Bosses at web streaming service Netflix have reportedly secured the rights to premiere the show worldwide in 2016.