The Queen's Sister (2005)

An in-depth biopic of Princess Margaret from the days following her father's death in 1952 until the 1970s. She was known to be a flamboyant royal but she remained a stickler for protocol. She had many controversial romances and also infamously kissed the daughter of the US ambassador. Also the film gives some focus on what others thought of Margaret, from normal people of the era to a backbench MP opposed to her 1961 wedding.