Guy Lodge reviews Thomas-Symonds' political biography of Clement Attlee, discovering a man fitting neither cult hero nor 'little mouse' whose government left perhaps the most enduring legacy of any British premier.

Most governments try to make a difference to the course of history, but only a very few succeed. In Britain since 1832, such landmark governments include the war-time premierships of Lloyd George and Churchill and the peacetime administrations of Peel, Gladstone (1868-74), Disraeli, Asquith, Attlee and Thatcher.

Of this elite club, the Attlee government of 1945-51 can claim to be the most creative, and can perhaps boast the most enduring historic legacy. In just six years, the Attlee government built the welfare state, including the jewel in the crown of its New Jerusalem - the national health service - replaced the failed laissez-faire economic orthodoxy of the 1930s with Keynesianism and a programme of nationalisation, decolonised large swathes of the British empire, and committed Britain to the Atlanticism that has defined British foreign policy ever since.

Such achievements are all the more remarkable when you consider that austerity-era Britain was bankrupted by war and immediately faced a new and dangerous enemy in the Soviet Union. Indeed, the Attlee government's true sign of greatness is that rather than succumbing to adverse circumstances, it capitalised on them. But self-evidently it was not an unalloyed triumph. In 1951, Labour lost and was consigned to the political wilderness for 13 years, with the unity of the Attlee era giving way to the civil war that broke out between the Gaitskellites and Bevanites.

Nonetheless, to paraphrase Churchill, this was unquestionably Labour's finest hour. But how much of this can be attributed to the leadership of Clement Attlee himself? This is the question at the heart of Nicklaus Thomas-Symonds excellent biography Attlee: A Life in Politics, which was published in paperback earlier this year. It is an important question to ask, since while Attlee's reputation has soared in recent years - he was voted the greatest modern prime minister by a group of political scientists in 2004 - he remains, in the words, of Vernon Bogdanor, 'the enigma of British 20th-century history'. Tellingly, we tend to speak almost exclusively about the Attlee government and rarely about Attlee the prime minister - and less still about Attlee the political leader.

Attlee's elusiveness was a defining feature of his career. Labour historian Kenneth Morgan has argued that the label of the 'Unknown Prime Minister', attached posthumously to Andrew Bonar-Law, is more appropriate for Attlee on the day of Labour's landslide, on account of his low public profile. Hence Thomas-Symonds' fair comment that, while historians might disagree on the causes behind Labour's great electoral triumph, in none of the competing interpretations 'is the victory attributed even in part to him'.

The Attlee that emerges in this illuminating study is neither the cult figure he has become, nor the colourless politician he was derided for being throughout his life. There is scant evidence here to support Hugh Dalton's charge that Attlee was a 'little mouse'. For a mouse, the laconic Attlee could be ruthless when required: on one occasion, asked why he was dismissing one of his ministers, he stared back and said 'you don't measure up to the job'. RAB Butler, who served with him during the war-time coalition, said he had 'a habit of biting people in the pants' if they turned up to cabinet meetings poorly briefed. Nor could he conceal his profound disdain for Ramsay MacDonald and the failure of his National government to address soaring levels of unemployment: 'the government' he said 'took over one of our misfortunes - the prime minister'.

Like Orwell, Attlee is best thought of as a patriotic socialist. Driven by a deep a sense of duty he immediately enlisted at the outbreak of the Great War, and witnessed the horrors of that conflict first in Gallipoli and then in Mesopotamia. He had no truck with the pacifism of MacDonald and Lansbury, and as leader (with Bevin's support) adroitly and painstakingly moved Labour behind the cause of collective security and rearmament. Like Orwell, however, he believed that the war effort was justified by more than the need to defeat Hitler: to be truly worth the human sacrifice, victory demanded winning the peace too.

This, of course, did not stop Orwell lamenting what he considered to be the timidity of Attlee's post-war programme. Notwithstanding this upset, the gap between the moderation Attlee embodied and the socialist 'revolution' Orwell prophesied should not be exaggerated. True, Orwell became suspicious of Attlee's statism, but fundamentally both form part of the English socialist tradition that was rooted in - and celebrated the innate decency of - ordinary people. If Orwell discovered socialism on the road to Wigan pier, Attlee's conversion happened at the Stepney boys' club, where he observed up close the poverty that blighted the East End. Their socialism, like that of Tawney and Morris, was ethical, not theoretical. 'The intelligentsia', Attlee declared, in words that could easily have come from Orwell, 'can be trusted to take the wrong view on any subject.'

In the present book, Thomas-Symonds shows how Attlee was able to get to and then stay at the top of British politics for as long as he did - his 20-year leadership was the longest of any political party in the 20th century - through a combination of real ability and some remarkable luck. These two factors obviously feed off and reinforce each other, but fortune undoubtedly played a pivotal role in Attlee's political life.

Had he, like most other ministers from the 1929-31 government, lost his seat in Labour's catastrophic defeat of 1931, when it was reduced to a rump of just 51 MPs, Thomas-Symonds says Attlee's star would have shone much less brightly. The 1931 result not only had the effect of catapulting Attlee from relative obscurity to the senior ranks of the party, paving the way for his leadership bid in 1935, but also ensured that in the 1935 contest few believed they were being asked to elect a potential Labour prime minister. Instead, the author argues, the party was being asked to choose a caretaker figure to lead the party through to the next election, which he rightly contends Labour would have lost, precipitating Attlee's demise. Had war not intervened to postpone an election in 1940 (or earlier) there would have been no Attlee premiership.

Above all Attlee was lucky that his two main rivals for the leadership - Ernest Bevin and Herbert Morrison - were bitter enemies who preferred to serve under him than each other. Had this not been the case, it is unlikely that Attlee would have ever entered Downing Street.

There is another important respect in which it might be said Attlee got lucky, which Thomas-Symonds does not touch on. There were structural factors in place that meant it was comparatively easier for Attlee and his ministers to achieve the political transformation they did. The foundations of the welfare state had been laid by Asquith's government, which faced much greater resistance from the forces of reaction than did Attlee in 1945. The British Medical Association (BMA) was nothing compared to the ferocious opposition provided by Unionist politicians, the House of Lords, the City and even the King himself during 1909-11. Thomas-Symonds fails to acknowledge the debt post-war Labour owed to the pre-war Edwardian left, which in vital respects helped to remove the ideological and institutional barriers to progressive reform.

Nor does he sufficiently acknowledge the extent to which the planned economy that emerged during the war and the important social reform achieved by the wartime coalition, especially the ideas encapsulated in the Beveridge report, meant that Attlee was tapping into the prevailing zeitgeist. These factors, combined with an idealism generated under wartime conditions, the presence of a largely homogenous manual work class, and a responsible trade union movement, all increased the wave that Attlee was able to ride. None of this meant the accomplishments of his government were inevitable - there were significant contingent factors he had to contend with, not least the desperate state of the nation's finances - but they nevertheless ensured the potential for a lasting legacy.

Attlee subscribed to Bagehot's view that democracy was 'government by discussion' and believed that the role of the prime minister was to steer such discussion to a firm conclusion. 'The essential qualities of the PM,' wrote Attlee, 'is that he should be a good chairman able to get others to work.' He might have added and 'keep warring ministers apart', since Attlee demonstrated remarkable skill not only in getting the most out of the political giants that sat round his cabinet table - it was, after Asquith's cabinet, the second most able in British history - but also, until the tail-end of his leadership at least, in holding his famously fissiparous party together. Attlee achieved the unity that has eluded all other Labour leaders precisely because he did not worry about being outshone by the likes of Bevin, Morrison, Cripps and Dalton. 'The secret of Attlee's success,' observed Jim Callaghan, 'is that he never pretended to be anything other than himself.'

However, as Thomas-Symonds shows, Attlee's personal style and hands-off approach to the premiership was a double-edged sword, responsible for both the triumphs and failures of his government. His careful management of Bevan throughout his fraught negotiations with the BMA was critical to the successful launch of the NHS. But Attlee's failure to provide sufficient leadership during the coal shortage crisis in the winter of 1947 and the convertibility crisis of that same year, increasing the burden of rationing on the public, badly damaged his government's reputation. It also nearly cost him his own job, had Cripps' plot to bring him down not been thwarted by Bevin. 'There was no leadership, no grip, no decision,' complained Cripps, underlining the fact that even in the late 1940s prime ministers needed to be seen to lead from the front and not just to delegate responsibility to cabinet ministers.

It is also questionable whether Bevin was right that Attlee's quiet public persona and reserved character suited this period - he believed the public were tired of the pugnacious style of the MacDonalds and Churchills of Britain's recent past - since he was plagued with questions about his leadership for the whole time he was in charge of the party. He faced three leadership coups, including one on the day of Labour's victory in 1945, when Morrison moved against him in an act which hardly represented a vote of confidence in the new prime minister. Harold Nicholson, the diplomat, best summed up Attlee's principal weakness when he described him as 'a delightful man ... but not a pilot in a hurricane'.

And so it proved, especially after the debacle of 1947, when faltering leadership combined with poor health to deprive the government of its initial cohesion. When Bevan and Gaitskell squared up to each other over how to cover the cost of rearmament in 1951, Attlee could no longer work his magic, and conspicuously failed to stand up to Gaitskell's intransigence, forcing Bevan's resignation.

Historic counterfactuals are an overused device, but nevertheless two seem particularly relevant in the case of Attlee's leadership. The first is to ask how successful his government would have been had he not been blessed with such political heavyweights as Morrison and Bevin. It is difficult to resist concluding that, without such figures, Attlee and his premiership would have struggled to achieve the landmark status it did. But equally, what would have been the fate of the government had Attlee himself not been at the helm? This second counterfactual underlines the centrality of his leadership to the success of his government, since a Morrison or Bevin premiership would in all likelihood have descended into internecine warfare that has been the trademark of previous and subsequent Labour governments.

Ultimately, Attlee's real failing - and something Thomas-Symonds overlooks - is that while he was the right man to implement Labour's 1945 manifesto, he lacked the necessary attributes to spearhead a renewal of Labour's agenda once the main planks of that programme had been put in place. This explains why his government soon ran out of steam and why Morrison had to concede at the 1949 party conference that whereas 'there was 40 years of thought' behind Labour's 1945 manifesto, establishing a fresh programme 'is not quite so simple as the task was' then.

Contrary to the popular idea that the Attlee government marked the dawn of a new era, it was understood at the time, especially by those involved, to represent the end of an old one. As Kenneth Morgan has argued, this cabinet of veterans regarded themselves as being present 'at a climacteric of history', able to finally realise the dreams of the party's early pioneers. Labour lost - and Attlee has to take the lion's share of responsibility for this - because the party had by 1951 proved incapable of recovering its sense of purpose.