In April 1946, the Attorney General, Sir Hartley Shawcross, told Conservative MPs in a Commons debate, “We are the masters” and will be “for a long time to come”. Labour had just become the party of the nation for the first time, with millions of middle-class voters supporting its offer of a very “reasonable revolution”. Shawcross appeared to embody the party’s newfound cross-class appeal. The son of a university lecturer and Liberal suffragette, he had been educated at Dulwich College before becoming a lawyer, where his “gifts of mind, tongue and assiduity marked him out”.

Impressing as Britain’s chief prosecutor at the Nuremberg trials, he joined a growing band of Labour MPs who looked and sounded like the “masters” of all they surveyed. Its leaders, from public school educated Clement Attlee (Haileybury) to Hugh Dalton (Eton), Sir Stafford Cripps and Hugh Gaitskell (Winchester), looked comfortable handling the levers of power. One newly elected MP confidently predicted” “We are going to be in for 20 years.”

However, amidst the triumphalism came an early warning from the man who had made the landslide happen. Just a few weeks after Shawcross declared Labour “the masters”, Herbert Morrison delivered a speech to mark the first anniversary of the 45 victory. He reminded his party that it needed to “hold the working-class electors, win the middle-class electors and make deep inroads into the rural constituencies”. Without doing so, “we are lost”.

Throughout the Attlee years, substantial media attention was placed on middle-class concerns

In February 1950, Morrison’s fears came to fruition. At the first chance of re-election, Labour’s majority dropped from 146 to an unworkable five. Despite adding over one million voters to their cause, the party suffered from the effects of a boundary review. Crucially – in what was dubbed the “revolt of the suburbs” – there were substantial swings against them in London, the Home Counties, Essex and Middlesex. By the end of 1951, Churchill was back as prime minister. Labour’s hopes of becoming a national party had all but disappeared.

When Labour now invokes the spirit of 1945 – as Keir Starmer did last week – it is often forgotten how quickly its support within the middle class fell away. Building and maintaining an electoral coalition between the working- and middle-class voters has evaded most leaders ever since. Even the successful ones – Harold Wilson and Tony Blair – are accused of favouring one group over the other.

1945 was supposed to be different. Idealistically, Morrison believed that the government could create a classless society. He talked of Labour being a third way between reactionary communist and Conservative ideologies: “The best answer to communist conceptions of unhealthy or violent class war and the Conservative champions of privilege is to break down the barriers which separate the classes.” In practice, this meant an economic “levelling up” – a phrase Attlee used long before it was taken up by Boris Johnson. He told voters that: “If you were right at the top you were levelled down. If you were down you were levelled up. If you were in the middle you are about where you were.”

For all Labour’s hopes of creating a more classless society, Britain remained divided about the future

Levelling up held an obvious appeal in Labour’s working-class heartlands. In an early attempt at a Harold Macmillan-style, “you’ve never had it so good” speech, Hartley Shawcross used his constituency rugby league team to highlight the new working-class affluence: “Next Saturday 12,500 St Helens people will be going over to Salford” for a cup match at the cost of 10s a head. “Do you think that there were 12,500 supporters who could afford it in 1938?”. Woodrow Wyatt was equally confident that Labour had a strong record to defend. Offering advice to first-time canvassers, he wrote that if they encountered a “Don’t Know” on the doorstep, they should ask the voter to think “Am I better off on the whole today than I was before the war?”. If they were working class, the only “honest answer” would be “yes” – meaning the conversation would be flowing in the right direction.

Labour’s appeal to its new middle-class voters was less obvious. The effects of austerity and inflation had hit middle incomes hard. Throughout the Attlee years, substantial media attention was placed on their concerns. Popular commentators such as Frank Owen wrote that the middle class was “the meat in the political sandwich” and had a “rough time” under Labour. Bread and powdered egg rationing were incredibly unpopular. Such measures led The Daily Mail to declare by 1947 that the “honeymoon was over”.

Shadow Ministers such as Harold Macmillan took advantage and warned that the “socialist” budgets had “swindled” the middle “out of a large part of their life savings”, but it was not just the Conservative side raising such issues. The Labour MP Richard Stokes urged the party to do something about the “professional men, the technicians and managers of all grades”. This group were the “backbone” of the nation – but under Labour were worse off than before the war. This, he argued, means “incentive to harder work is gone”.

Just as in 1945, Herbert Morrison was seen as the man to win Middle England round. In a controversial speech in Margate, he warned his party that the middle class had stagnated: “A lot of them voted for us at the last election … they have suffered a painful and difficult reduction in their living standards.” It would, he concluded, “do us no harm to remember these facts since we need their support again”.

This was a theme he would continue to return to. In Blackpool, he argued, “we need the so-called middle class and we must try to understand their problems, talk to them in language they understand and get them behind us”. He launched an appeal for them to join Labour’s ranks and help shape the debate: “Do not stand aside. Do not merely sulk and grumble. Come into the Labour Party”. Privately, he told a PLP meeting that they all needed to be “kinder” to the middle class. In Scotland, he urged party members to use “heads as well as emotions” to win rural voters back.

Speaking “kindly” and “using heads over emotions” did not come naturally to the Labour figures who had long used class warfare rhetoric. Nye Bevan was the “bogeyman” of the right-wing press, and happily gave them ammunition. In a speech in Coventry, he argued that, “There are many people in this country worse off than before the war.” This was good: “We always intended that they should be. We never said that a Labour Government would be good to everyone.” Infamously, he caused a stir when he referred to the Conservative Party as “lower than vermin” – an incident that was (literally) worn as a badge of honour by some Tories.

In the end, such appeals were not enough to reassure the middle class of a more prosperous future

Bevan was not alone in rejecting Morrison’s appeals for softer words to Middle England. At Margate, Manny Shinwell declared that Labour represents “the workers by word and brain. As for the others it does not matter two hoots”. Backbencher Ian Mikardo likened Labour’s spending on military – in the face of austerity – to the “stuck-up middle-class housewife who got into debt not through buying food for the family, but to get posh new curtains for the front windows”. Such talk, as Mary Sutherland was keen to point out, was careless. Any serious party had to pay great attention to “the woman’s vote” because “in any constituency, housekeeping – not mining or agriculture or textiles – is the biggest single occupation.”

When the U.S journalist Theodore H. White visited London in 1949, he found that Britain was still divided along class lines. In Mayfair, he was told of a “sour” feeling towards the post-war reforms. But when he visited a new council estate in East London, he found pubs heaving with new working-class affluence: “Boys singing in high pitched tenor voice, old women in the corners and the young people singing and dancing in the middle of the room.” Labour’s re-election chances, he concluded, hinged on a gamble, not on the facts of its programme, “but how facts affect people.”

To understand whether Attlee’s administration had truly levelled up, Picture Post magazine sent a reporter to the seat with the highest Conservative majority (Bournemouth) and the strongest Labour one (Dearne Valley). Overall, they found that “the people of each constituency are now, in some sense, prosperous”. Yet, the industries that shaped the people – and their priorities – were still different.

Dearne Valley had hugely benefited from coal nationalisation. “It’s fabulous money they’re drawing now,” observed one pub landlord. Bournemouth’s leading trade on the other hand was the hotel and boarding house sector and there were only a handful of new factories. The traditional Conservative voter viewed these “quizzically”, at best “irrelevant to the bona fide Bournemouth” and at worst “a wild menace” to its tourist economy. Nationalisation had not greatly impacted the workforce.

For all Labour’s hopes of creating a more classless society, Britain remained divided about the future. In July 1949, the pollster Mark Abrams found that all electors except Conservative ones believed a Conservative victory would lead to “more industrial disputes” and an extension of “private enterprise”. Conversely, all but Labour supporters believed a Labour victory would lead to a “neglect of national material prosperity”.

When the election began in January 1950, the bookmakers made Labour the 4/7 favourites for victory. Attlee declared: “We have confirmed faith in democracy by the example of a government that has carried out its promises.” However, candidates quickly sensed fatigue amongst an austerity-battered electorate.

Labour spent the rest of the 1950s trying to work out how to appeal to the new affluent voter

In Leicester, Attlee was met with “catcalls” and chants of “vermin” when he called for both parties “to live together and love one another”. On another occasion, in Enfield, Hugh Gaitskell spent a meeting “trying to keep the temperature down” after facing a barrage of abuse from housewives who were worried about “dirty coal”. When one of them claimed the miners were too highly paid, were “too soft” and “take days off to go to the races”, Gaitskell almost walked out. “I am not going to stand here and hear the miners insulted”. He sensed there was now “a collection of grievances among the lower middle class and middle class” against Labour.

Herbert Morrison still pulled in crowds, but Hugh Dalton was disappointed to find himself addressing half-full halls. When three American journalists held a meeting in London to discuss the state of the race, an audience member replied that, “You Americans are far more interested in the election than any English people I’ve seen.”

In Kent, Morrison reminded voters that the welfare state’s benefits should be factored into their calculation of living costs. He believed voters had a “sense of pride” that “we have abolished destitution among poorer people”. In Birkenhead, Shawcross accepted that the middle class were “sorely burdened at present”, but that it was worthwhile because Labour was “trying to promote the interest of the community as a whole”.

In the end, such appeals were not enough to reassure the middle class of a more prosperous future. The Conservative manifesto This Is The Road accepted the new welfare state’s foundations but focused on the loss of freedom since 1945. Churchill claimed Attlee had not “levelled up” but had actually “levelled down”. “The choice,” he claimed, “is between two ways of life … between a policy of levelling down and a policy of finding opportunity for all to rise upwards from a basic standard”.

Freedom was central to the Conservative message. In one poster, the party joked that the Chancellor took seventeen cigarettes out of a pack for every one smoked by a voter. In Dartford, the young Margaret Roberts (who married Denis Thatcher in 1951) offered Labour a glimpse into the future. She promised to champion the voiceless “small shopkeepers” who formed “the strength and backbone of England”. In words that would become so familiar to the public over the course of the 1980s, she argued that socialism would always neglect free enterprise.

When the results came in, Morrison cheerily declared that, “The British people are wonderful, they didn’t mean to chuck us out, only to give us a sharp kick in the pants.” Soon they would be chucked out, and Labour spent the rest of the 1950s trying to work out how to appeal to the new “affluent voter”.

At first glance, the task facing Keir Starmer in the 2020s is the opposite of that facing Attlee, Morrison and Shawcross in the 1940s. At the next election, Labour will have to win back the voters in the ex-mining towns that turned away from them for the first time in in a generation. At the same time, Labour must hold on to the new heartlands in London and the South to have any hope of victory. In practice, however, Starmer faces the same problem that all Labour leaders must address: finding the words, the stories, the individuals and the policies to bring both working and middle class voters behind Labour on election day. As the events of 1950 showed, it is a task that even Clement Attlee found daunting.