Daily catch-up: 'a lot of clever people failed to see the essential problem with the poll tax'

To the Strand Group at King's College, London, last night to hear Charles Moore talk about the second volume of his biography of Margaret Thatcher. The book covers the story from 1982 to the 1987 election, at which the Conservatives promised to bring in the poll tax. Moore said: "A lot of clever people failed to see the essential problem, which was that if you invent a new tax that millions of new people are going to pay, how do you think they are going to react?"

Which does make one wonder how George Osborne, David Cameron and the undeniably clever people around them have got themselves into the tax credits mess. It happened partly because Osborne expected the cuts to be palliated in negotiation with the Liberal Democrats, and partly because, one suspects, when he found himself with an unexpectedly free hand, he learned the wrong lesson from the history of the Thatcher government. He might have thought he should take bold and painful decisions early on, as Geoffrey Howe did in his 1979 Budget. But to concentrate the losses on low-paid people in work, a group containing large numbers of swing voters, was probably a mistake and a U-turn is likely in next month's Autumn Statement.

Moore repeated his view that Thatcher lied to the House of Commons about the leak of the Solicitor General's letter on Westland. She said in the Commons that she had not been consulted about the leak, whereas Moore said: "It was basically done on her orders." That led to the farce of Sir Robert Armstrong, the Cabinet Secretary, being asked to carry out "an inquiry in order not to find out what happened", which Moore said he did brilliantly.

I find this remarkable. It was of course suspected at the time, by people who didn't like Thatcher, that she was behind the leak. Even now it cannot be proved that she ordered it. But it is important that Moore, her official and sympathetic biographer, makes that judgement.

In answers to questions, Moore said that the surprising thing about Thatcher was that she was "extremely disorderly". Her conduct of meetings was haphazard and she was liable to distract herself by pursuing irrelevant lines of discussion. "Every single thing she said and wrote was like a citizen – she was not captured by government." She was bad at remembering who was responsible for what, and was no respecter of hierarchy, which meant she often upset people. "She was a disruptive force."

Much of this volume is about foreign policy. "She was an absolutely key figure in the history of the world in this period," said Moore. She was close to Ronald Reagan, yet they had a fundamental disagreement on nuclear weapons, one of the most important questions. "He detested nuclear weapons and wanted to get rid of them altogether; she believed in them and believed in deterrence theory." Moore thought she handled Reagan astutely, becoming a player in US politics, divided as the White House, Pentagon and State Department always are. "Each of them wanted to invoke Margaret Thatcher for their own ends because Reagan liked her so much," giving her scope to influence his policy.

Finally, Moore talked about the criticism of her, made by John Hoskyns, the business person who was an early head of her Policy Unit, that she had no strategy. "Business is essentially a rational occupation; politics is essentially an irrational one. She didn't have a strategy, she had a will. She had a purpose, an emanation of will, which was felt throughout Whitehall and which made things happen."