Peter Hennessy's latest volume in his history of Britain was a little late, but, he tells Huw Richards, he wished to capture not only the politics but also the smell of coal smoke.

Historians were ever wont to form factions, but Peter Hennessy may be the first to claim membership of the "Max Bygraves school of history". His adoption of Bygrave's catchphrase - "I want to tell you a story" - is timely. The latest story told by Hennessy, professor of contemporary British history at Queen Mary, University of London, is that of Britain in the 1950s, when the entertainer was at his peak.

Hennessy's latest book is Having It So Good . The title is derived from yet another catchphrase, the claim in 1957 by Harold MacMillan, then Prime Minister, that "most of our people have never had it so good". It is the second volume of a history of Britain from 1945 to 1990 that was first envisaged as a three-parter but has mushroomed into five works, their production a personal and publishing marathon.

The first volume, Never Again , was published in 1992. "The original idea was to have all three volumes completed by the millennium," Hennessy recalls. This is not the academic tardiness it might appear; three substantial works of political history, The Hidden Wiring (1995), The Prime Minister (2000) and The Secret State (2002), claimed Hennessy's attention in the period.

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That 14-year hiatus has had an impact. "If I had written Having It So Good immediately after Never Again , it would have been a slimmer book, would have lacked a lot of material that has since become available and would have been written against a different background," he says. "While in theory it does not matter to a historian what is going on around him as he writes, of course it makes a difference."

Hennessy notes that he wrote Never Again , which centres on the struggles and achievements of Labour's immediate postwar Government, when many believed that Labour might never again be elected. Having It So Good 's chronicle of Conservative dominance has been accompanied by the Blair ascendancy.

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The Fifties tend to be seen as peaceful and rather dull. Hennessy disputes this - particularly the dullness: "For people who had come through the slump and the war in the previous 20 years, there was nothing dull about the first small signs of mass prosperity." He buries one myth about domestic peacefulness, pointing out that crime began rising sharply five years before the abolition of national service, which is often credited as the reason for low postwar offending rates.

As in Never Again , Hennessy is concerned to reflect everyday experience. "You want to capture the revealingly prosaic - the smell of coal smoke, elderly ladies in pacamacs - to have people who lived through the time say 'that's how it was', but at the same time also saying 'but I didn't know that'."

What they did not know was the detail of the high politics of the time as governments wrestled with Britain's diminished place in the world. As Hennessy describes MacMillan in 1959: "He might have deceived the electorate, but he had not altogether convinced himself."

He hopes that his trawling of government documents from the period allows him to take readers "into the Cabinet rooms and the discussions of the time". The temptation to be avoided is that created by 50 years of retrospect. "It would be easy, and completely wrong, to shout at them about what it now seems obvious they were doing wrong."

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Although the book's tone is made sombre by the ever-looming atomic bomb, that is leavened by Hennessy's eye for anecdotes, which include the in vino veritas performance of the interpreter for the Soviet leader Nikita Khrushchev during a state visit and MacMillan's lament about meetings with Geoffrey Fisher, then Archbishop of Canterbury: "I want to talk about religion, but he only seems interested in politics."

Britain's rulers emerge well from his scrutiny. Alongside Anthony Eden's well-remembered failure over Suez in 1956, Hennessy resurrects his long-forgotten enthusiasm for technical education. He also acknowledges MacMillan's seductive danger to the historian. "His diaries are gold, but he wielded such a turbo-charged pen that it would be very easy to fall into seeing every event from his perspective." But he also adds: "You realise how fortunate Britain was in 1959 to have two class acts such as MacMillan and [Labour leader] Hugh Gaitskell whose principle concern was what used to be called 'the condition of the people question'."

Hennessy, who made his journalistic name as a chronicler of Whitehall, is more interested than most historians in the Civil Service, which he sees at a peak of influence while being led by Cabinet Secretary Norman Brook - "he was everybody's chief adviser, and you see his influence everywhere" - and individuals such as Otto Clarke, father of Labour politician Charles.

When Hennessy talks of "a grown-up working relationship between mature politicians and officials who had gone through slump and war together and had learnt how to take hard decisions", the implied rebuke to Britain's 21st-century rulers is intentional.

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Suez and the atomic bomb dominate this volume, but two other government moments also stand out. Hennessy establishes the 1952 ROBOT plan to float the pound as one of the great might-have-beens of postwar history - "unemployment would have rocketed, and what we think of as the postwar consensus would have been over" - and the former lobby correspondent in him can only marvel at the fact that there were "three acrimonious Cabinet meetings" about it without a leak. The other big event is the 1959 Future Policy Study analysing Britain's place in the world after Suez, the clear-eyed document that occasioned MacMillan's inner disquiet. "It has only recently become available," Hennessy says, "although Sir Michael Carver tried very hard to get it published in the 1990s."

The third instalment of Hennessy's five volumes, on the 1960s, may, like the second, be some time coming. His next project, a history of British intelligence in the Cold War, has been made urgent by the age of many key witnesses. It is likely to take six years, at which point he would be 65 with three volumes of postwar history to come. While explaining that his daughter Polly - a history graduate and publisher - has promised to warn him should he start losing his touch, he is undaunted by the implied timescale. Bygraves, after all, is still performing at 83.

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Having It So Good is published next week by Allen Lane, ?30.00.