In June 1968, 187 women sewing machinists, employed to make car seat covers in the Ford factory at Dagenham, took a stand against the downgrading of their jobs as “unskilled”. Going on strike for equal pay with their male colleagues, they brought production at Europe’s largest factory to a standstill.

It is not the most momentous event of that tumultuous summer of 1968 and as the subject matter for a film it feels like it should inspire a piece of low budget, activist cinema. Instead it forms the raw material for a new comedy drama, Made in Dagenham, that even the case-hardened critic Mark Kermode has called “genuinely feelgood”. William Ivory, who wrote the screenplay, is known for giving space to working-class lives on TV series such as Minder and Common as Muck, but his work is far from being agitprop. “If you want to pull the rug from under people,” he has said of his own liking for warm, audience-engaging narratives, “you’ve got to get them on the rug first.”

Through what strange alchemy has the fractious politics of postwar industrial relations been transformed into mainstream entertainment? Of course it helps that the film is set in the past, looking back on a world whose conflicts have ceased to perplex and divide audiences. In today’s largely deregulated, de-unionised workplace, striking workers are not the scapegoats of the financial crisis as they were for many in the economic downturn that began in the late 1960s. Along with its retrochic Biba dresses and Ford Cortinas, the film implicitly references a lost tradition in British film, which used a familiar setting that guaranteed narrative conflict: the shop floor. These films are almost our equivalent of the American western, in their tense picket-line showdowns, their struggles between individual conscience and group loyalty, and their evocation of a lost world of moral certainties and life-or-death struggles. As with the western, they were more concerned with neurotically reworking national anxieties than representing historical reality.

It took some time for these generic conventions to develop. During the most depressed and difficult years of the last century, cinematic representations of the factory were surprisingly celebratory. In Sing as We Go (1933), Gracie Fields leads a chorus of the title song as she marches her fellow millworkers through the factory gates on their way to the dole queue. Wartime propaganda films such as Night Shift (1942), Keep the Wheels Turning (1942) and Millions Like Us (1943) were meant to act like incantations, stressing worker camaraderie and pride in manual labour in the hope that these things would rub off on real factories.

You can already see the bonds of wartime solidarity dissolving in the Ealing comedy The Man in the White Suit (1951) in which Alec Guinness plays a laboratory dishwasher at a Lancashire textile mill who invents an everlasting, dirt-repelling fabric. In Sing as We Go, workers and bosses alike embrace modernity in the form a new artificial silk which allows the factory to reopen; in The Man in the White Suit, the workers and mill owners, fearful for their jobs and profits, unite against the white-suited entrepreneur.

As the 1950s wore on, labour relations deteriorated. Car workers generated particular middle-class resentment because they were among the highest paid manual workers in the country, and the most militant. The Ford plant at Dagenham saw 235 walkouts in the space of two years.  An idea of the proletariat as a shirker and troublemaker started to solidify. “The natural rhythm of the British worker,” says the time-and-motion expert, played by John le Mesurier, in I’m All Right, Jack (1959), “is neither natural, rhythmic, or much to do with work.” That this film is misremembered as an attack on the trades unions and their shiftless, inefficient members is largely down to a performance of virtuoso naturalism from Peter Sellers as the shop steward, Fred Kite.

From his first scene, when he marches across the yard with his flunkies to accuse Terry-Thomas of “jeropardising the safety of employees”, Kite is both authentically dull and weirdly hypnotic. He is also a complex and even touching creation who allows us to glimpse the tiny seed of idealism – his dreams of the Soviet Union (“all them cornfields and ballet in the evenings”) and warm memories of a Balliol summer school – from which his gigantic obsession with procedure has grown. If anything, the film is harder on the bosses, who are embroiled in a fraudulent arms deal, than it is on the pigheaded, well-meaning Kite. But Sellers steals the film so completely that it throws the agnostic, universally cynical politics of the script out of kilter.

The same anti-union slant skews The Angry Silence, made the following year, in which Richard Attenborough plays a factory worker persecuted by his colleagues for refusing to join an unofficial strike. Managers are venal and corrupt here as well, but they are shadowy figures while the workers are drawn in primary colours. What these films thus fail to convey is the widely felt sense at the time that the “British disease” of seemingly terminal economic decline was as much to do with directionless, hidebound management as the workshy proletariat. Michael Shanks’s bestselling 1961 book, The Stagnant Society, was typical in seeing management and unions, horsetrading with each other, as the combined forces of conservatism. Bolshy shop stewards were just the symptom of a wider pathology: a backward-looking culture mired in stale traditions.

“Britain is not, contrary to frequent impressions, a country very prone to strikes,” insisted Anthony Sampson in his 1962 book Anatomy of Britain. The popular perception was quite different, largely because of the wide publicity given to wildcat, unofficial stoppages. A popular caricature of the era was the shop steward with a Napoleon complex who would pounce on a minor problem, such as a cup of canteen tea judged wanting by a trade union tea taster, and order members to down tools. “Everybody out!”, the catchphrase of Paddy the obstreperous female shop steward in the 1960s sitcom The Rag Trade, brought this caricature into millions of living rooms.

When the Carry On franchise latched on to this idea, it was clear that it had become part of the reservoir of shared national clichés. In Carry On at Your Convenience (1971), Kenneth Cope plays Vic Spanner, a shop steward with a Che Guevara moustache and a moped: Fred Kite without the hinterland. When his struggling lavatory firm secures an order for bidets, Spanner calls the workers out because this involves tap fitters and waste pipe fitters doing each other’s jobs. The alien, continental bidet serves as a metaphor for the inability of the British worker to embrace change; wedded to restrictive practices, Spanner blithely leads the country down the toilet.

Spanner’s chief crime, like Kite’s, is to have no sense of humour. The historian Ross McKibbin argues that in these years the middle classes came to identify themselves through a code of good manners and wry humour which set them off from what they saw as the aggressively assertive working classes. It was the workers and the unions who dragged politics into human relationships and took everything so seriously. Spanner’s antithesis is Sid James as the factory foreman: all pipe, pullovers and reassuring laugh, he is there to suggest that the country needs to put its sectional antagonisms aside and pull together in a display of common sense and good humour. But the film was a box office disaster, suggesting that the Carry On team misread their largely working-class audience, who were not as virulently anti-union as the tabloid newspapers they read. They would probably still have gone to see it if it had been remotely funny – instead of tired and retrograde like the British industry it was satirising.

By 1971, Vic Spanner was almost as dated a stereotype as the Khasi in Carry On Up the Kyber. Although Edward Heath’s Industrial Relations Act of that year, which made unofficial strikes illegal, was never properly implemented, there was now a broad political consensus that union power should be curbed. Mike Yarwood still impersonated union leaders on television, a sign of their continued cultural prominence. But the postwar heyday of the shop steward had passed, some years before the now mythologised winter of discontent. The Thatcherite reforms of the trades unions, which banned secondary picketing and made strike ballots compulsory, have rendered the picket line extinct as a source of narrative tension in film, except in period pieces like Made in Dagenham. Mainstream films depicting working-class life in the post-Thatcher years, like Brassed Off and The Full Monty, were about unemployment, not work.

But perhaps the link between history and its filmic representation is more complicated than this. In our collective memory of the pre-Thatcher years, we imagine “the unions” as an endemic problem afflicting the whole of British society. In reality, militancy was confined to specific, highly visible areas of the economy. And some of the most difficult labour relations were in the film, television and newspaper industries – which meant that the directors, writers and editors who controlled popular representations of the unions were the most likely to be irritated by them.

The Boulting brothers were in dispute with the cinematographic unions for years because they combined the roles of editors, directors and camera technicians, and work on I’m All Right, Jack was suspended at one point because they had not paid their union dues. They based Fred Kite on a bumptious rep in the Electrical Trades Union who worked at Shepperton film studios; Sellers drew on the mannerisms of another shop steward at Shepperton who was, he said, the type who “rushes about with a little notice board in his hands and a list of names on a sheet of paper fastened on with paper clips”. Carry On shoots were often halted by shop stewards: for the producer, Peter Rogers, there may have been an element of wish fulfilment when, at the end of Carry On at Your Convenience, Vic Spanner’s mother bends him over her knee and spanks him. Such problems are unlikely to have afflicted the makers of Made in Dagenham. In recent years, Hollywood producers have flocked across the Atlantic to escape their own heavily unionised technicians and work with cheap, flexible and obliging British film crews.

Made in Dagenham skirts lightly over the more divisive aspects of postwar industrial relations: it is not about Spanish practices or picket line intimidation but equal pay, an issue on which everyone now agrees. The casual misogyny of 1968 is a painless thing for a cinema-goer to pass judgment on in 2010. The producer, Stephen Woolley, was inspired to make the film by an edition of the Radio 4 programme The Reunion which brought the women machinists together 40 years on. “What struck me in particular was how innocent and unpoliticised they were,” he says. “All they wanted was a fair deal.” As in Calendar Girls – which shares the same director, Nigel Cole – a group of essentially apolitical women grow as characters as they are dragged along by events. The opening of the film outlines their separateness from the male-dominated assembly line: they are working not in the main plant but a mile or so away in a leaky hanger made of asbestos. They are not part of the conventional struggles of the late 1960s, and are drawn into them grudgingly.

Inevitably, films have neater endings than in real life. The actual Dagenham sewers went back to work not with equal pay but just seven more pence an hour. Although the dispute led to Barbara Castle’s Equal Pay Act of 1970, this was no help to the women machinists, who were not doing comparable work to their male counterparts. Car seats today are moulded and don’t need anyone to sew their covers. The machinists’ jobs have disappeared into the globalised, outsourced ether along with much of the work at Ford Dagenham. And it’s hard to make a feelgood film about that.