Netflix's The Crown is a series based on true events, but with a level of detail it is not possible to know. The series are all focused around real moments in British history, like the invasion of the Falklands, the marriage of Charles and Diana and the break in at Buckingham Palace. But we can't know the exact details of the conversations had between the various members of the Royal Family. There have been some episodes which feature historial inaccuracies, for example, characters appearing who had already died at the same point in real life. The Crown does provide a bit of information about life in Britain over five decades, but it's not a documentary.