It is 70 years since Clement Attlee formed his landmark Labour government after winning a 146-seat majority in July 1945. How distant such success seems to today’s party. These days, associating oneself with Attlee has become the equivalent of evoking God in the race for the Republican presidential nomination. God means different things to different people, however.

Jeremy Corbyn’s supporters see in Attlee both the victorious outsider and the embodiment of Ken Loach’s “spirit of ’45” – the moment when the British public showed it had just been waiting for a truly socialist agenda. Such comforting myths, recently recycled by Owen Jones, Billy Bragg and Clare Short, are not new. When Attlee’s majority was reduced to five seats in February 1950, despite Labour having won an even higher portion of the popular vote than in 1945, Richard Crossman consoled himself that 13 million people had voted for pure socialism. Forget the loss of more than a hundred seats – this was progress!

For the modernisers, Attlee’s success tells a different story: a victory dependent on its appeal to Middle England, which kept the “silly left” in its box, or on the back benches. The very persona of Attlee – his service in two wars, as a volunteer solider in the First World War, and as deputy to Churchill in wartime coalition – was a guarantee that the “New Jerusalem” was “not something exotic”, as Attlee put it, “but a natural evolution of the British desire for freedom”. The country defined itself against the crass popularism and extreme mood swings that had led its European neighbours to disaster.

Special pleading was anathema to the Attlee project. Everyone would benefit from a transformation of the relationship between state and society; but everyone would have to share the pain, too.

Two things are often forgotten about that government. The first is that it was notorious for price controls, rationing and austerity. The second is that the TUC – which used to think it was better to have a Labour government in power than a cowed party in permanent opposition – agreed to a freeze on wages for most of the government’s existence. “There is a limit to what any government can do,” Attlee also said in 1946. “We seek to set up the conditions in which fine lives can be lived, but the fineness of those lives depends on the ideals and conceptions of those people themselves.”

Most of the senior figures in Attlee’s first cabinet were in their mid-sixties. It was composed of men (Ellen Wilkinson, as minister of education, was the only woman in a senior role) who had spent their lives in the struggle, and had lived through two world wars (many serving, in some capacity, in both). For those such as Ernest Bevin, his chief lieutenant and foreign secretary, this was not a parlour game. Political power was hard won; elaborate self-definition and ideological purism could be left to malcontents on the back benches or in the universities.

Bevin and Attlee would have failed the type of “dinner-party test” applied to the left today on many counts – not least for their belief that Britain was a “great power or nothing”, and needed a nuclear weapon with a bloody great Union Jack on it.

The Labour Party of 1945 had other assets: intellectual depth (which did not mean conformity or consensus), historical literacy, patriotism and moral purpose. There is a dim, nagging recognition that Labour can no longer afford to sniff at these things. But it has lost the ability to talk in these terms without resorting to disingenuous folksy-speak. It is stuck between technocrats, who sound like automatons when they talk about their encounters with “real people” (remember Ed Miliband’s encounter with Gareth on Hampstead Heath?); and ­faddists, whose excitability and single-issue radicalism betrays the type of “we know what’s best” attitude that the electorate cannot abide.

It says much that the most serious debate so far between the leadership contenders has been between two former members of the same government about the extent to which the party should apologise for having run a deficit when it was last in office. If the Corbyn surge reflects one thing, it is a desire for something more than a race composed of functionaries or heads of former departmental caucuses.

Yet Corbynism is a retreat into the type of self-indulgent posturing that Attlee detested. When Attlee was wounded in Meso­potamia in 1916, he was both proud and tickled that he was hit by shrapnel while planting the red flag of his regiment in the enemy’s trench. In April 1939, on the eve of the Second World War, the self-appointed inheritors of the red flag on the left of the party tried to force Attlee out. Both Stafford Cripps and Aneurin Bevan called for a “popular front” with all the forces on the left (from radicals to communists). Attlee knew that such unpatriotic opportunism would destroy the labour movement; he also understood that the left would have a new obsession within a few months.

“The people’s flag is palest pink,” he quipped. “It’s not red blood but only ink.” That slogan should be stamped on the back of the “What would Clem do?” T-shirts that have become fashionable among Jeremy Corbyn’s supporters.

Clement Attlee’s great achievement, and the reason why he was a better leader than many brighter minds – such as Cripps or Bevan – was to steer the Labour Party away from periodic fits of badly timed, faddish radicalism and navel-gazing: to save it from itself. As he wrote in a private note in 1948, a true leader must have “an architectonic sense” – that is, he must see the whole building and not just the bricks. Corbyn would be his last choice.

John Bew, an NS contributing writer, is completing a biography of Clement Attlee