Video: Margaret Thatcher's authorised biography: her arrival at Downing Street Charles Moore, Margaret Thatcher's authorised biographer, says Downing Street was slightly unprepared for Britain's first woman prime minister and she herself was initially unsure how she should act. When you go through the door for the first time as Prime Minister, there is a real sense that you don't know where to go and you hand yourself over to the people who are already there. Of course with the first woman Prime Minister, there is even more of a question. How is she supposed to behave? She asked what am I supposed to do. The book, which is being serialised in The Telegraph, reveals hitherto unknown stories about Baroness Thatcher's years at the centre of politics.