Mrs Thatcher has now been in office for 3,167 days - overtaking Asquith as the longest serving Prime Minister this century. Only four premiers have now served longer terms - Robert Walpole , William Pitt the Younger and Lords Liverpool and Salisbury. Robert Harris, Political Editor of the Observer, looks at how the Prime Minister has stamped her personality on the government of Britain, and talks to more than a dozen men who have worked closely with her. Lord Hailsham on her place in history: 'You've got to put her in the same category as Bloody Mary, Elizabeth 1, Queen Anne and Queen Victoria.' Lord Havers on her ruthlessness: 'If she thinks a minister is no longer up t