If he did not seize the chance to invade Poland after winning the civil war in Russia, how would his regime survive without ally-states in central Europe? But if he threw the Red Army at the Poles, what would happen if the Polish troops defeated it and revolts continued in Russia?Ideology and personal impulsiveness came together, and Lenin chose to invade. Cromwell himself promoted a more expansive foreign policy than he appears to have wanted when he took power.Halliday's thesis is that new types of regime, which we usually call revolutionary, have the consequence of destabilising international relations. In his estimation, even the English Civil War - a process usually treated as impervious to influences from the European mainland - would have turned out differently if other powers had not been distracted by the effects of the Thirty Years' war. He adds that Cromwell's regime, by the very anti-dynastic principle of its creation, was bound to have an impact on English foreign policy and the policy of European powers towards England. His principal theme is the relationship between the domestic establishment of a revolutionary state and its international entanglements. The revolutionary leadership had little trouble in finding support for the overturning of law and tradition.Halliday is keen to add that, nearly always, revolutions also have an important foreign ingredient.

Each of them at the time had a leadership determined to turn its country upside down. The leaders were usually ruthless to the point of fanaticism and intent on propagating a message - an ideology or religion - that would set people free. Each revolution, too, was produced by deep tensions in the old society. Then Andy Warhol came up with a portrait of Mao that made him look like a tired circus performer.

When the Cold War ended, this satirical approach became a way of envisaging revolutions. TV adverts for lager dressed actors up as Stalin; Lenin lookalikes were photographed with tourists on Red Square. Revolutions no longer terrify us. William Hague's invocation to Tories to undertake a "common-sense revolution" shows that it is often the right that now employs revolutionary rhetoric. But, as Fred Halliday asserts in his new book, revolutions should be treated with circumspection. The rot set in with those T-shirts of Che Guevara in the Sixties; revolution became a fashion item. Now all he has to do is convince the country that he will ensure fair shares are distributed to everyone..

NOT SO long ago, revolutions had to be taken seriously. Mao's Little Red Book was examined for clues about Peking's domestic policies. Biographies of Robespierre were searched for hints about Soviet political practice. The English Civil War retained huge interest; there was endless debate on the contribution of Cromwell's rule to life in modern Britain All that seems like a bygone age. And social justice makes an appearance, with the pledge to create a new children's fund to help fight the "war on child poverty".The Chancellor closed his speech with traditional, headline-grabbing generosity: free television licences for everybody over 75. We might almost call that a redistributive measure, a little bit of fairness smuggled into a Budget for enterprise. What we have is a Chancellor for business, who has managed to convince most of his party that growing the cake is a recipe for feeding everyone at the table.