Her command of detail was legendary, helped by the fact that she could survive on four or five hours sleep. Woe betide anyone who was not as in command of a brief as she was. The worst thing an official could say to her was: "I dont know." Yet her approach to what is now called evidence-based policy was gloriously ambivalent. Told that a report from the Central Policy Review Staff CPRS was based on the facts, she retorted: "The facts! I have been elected to change the facts." Before long, she abolished the CPRS, a Whitehall think tank designed to serve the whole Cabinet, and replaced it with the current prime ministerial policy unit, which, as Lord Hennessy put it, "was hers to the last paperclip". A believer in lean government, she also abolished the Civil Service Department, which seemed to produce reams of management "guff" unrelated to policy and which was headed by Sir Ian Bancroft, whom she disliked.