Using unseen archive footage, new filming and interviews with those closest to the action, Michael Cockerell tells the inside story of the 20 years that took Margaret Thatcher from Commons new girl to her election in 1979 as the first ever female British prime minister. While her decade inside Number 10 has been well covered, the story of how she rose to the top has remained untold, and the film shows how she fought the male chauvinism of Westminster, particularly in her own party.