About 300 women in a pocket of inner London have just won a big victory in one of the most important battles of our time. They are Camden’s school catering workers or, as I used to call them in my days of ballpoint-pen-smeared shirts, dinner ladies. After months of protest they are finally earning the London living wage. That means a pay rise of £2.55 per hour, which, for the majority of the part-time staff, equals around £1,500 extra each school year. For a good number of them, that’s the difference between their families eating properly or going hungry.

I want to pass on their story because it’s a good one, and funny in parts. But most of all because it’s surprising – because, had you met these women even a few months ago, you might have considered their cause to be as good as lost.

Back then, Camden’s dinner ladies were on just above minimum pay. They ranked among the 4.9 million employees in this country who the Resolution Foundation describes as earning less than a living wage – a group that has swollen vastly in size since the banking crash. Analysts and trade unionists often depict low-paid work in strikingly similar terms: it’s low-skilled (however that’s measured), and done by people who aren’t in a trade union (or, rather, no union rep’s bothered to try to recruit them), and who work for an outsourcing firm that offers its clients low prices and gives its staff miserly pay. In this way, the position of low-paid workers in Britain is first described, then euphemised and finally rationalised. Meanwhile, the super-salaries paid to the richest 1% are usually passed off as the just reward for top talent.

However highfalutin the excuses made by a society for paying a few people millions and many, many more below subsistence, it doesn’t change the reality of living on crap wages. Ask Annie-Rose Barnes, central to the dinner ladies’ fight in Camden. Her mother is chronically ill, while her husband’s shoulder injury stops him plying his trade as a carpenter. With her poverty-pay job the family’s main source of income, Barnes had to support her teenage boy through school. She tots up the cost: “Uniforms, books, trips. He’s got size 10 feet and shoes don’t come cheap.”

She racked up an overdraft and other debts, fell behind on rent and stinted on her meals. Stress and a poor diet meant she dropped from a size 10 to a size six within two years. And still, she says, household basics became unaffordable discretionary items. “Sanitary towels,” is one example. “I’d use toilet tissues instead.”

It says something about 21st-century Britain that it can expect workers to leave their homes and slog it out in a hot kitchen and come back without enough money for a pack of Always. Still, according to the usual calculations, Barnes’s position would normally be deemed hopeless. She and her colleagues worked for an outsourced school-meals firm, Caterlink, which was under no contractual obligation from Camden council to pay staff any more. The women weren’t in any union – Barnes remembers that at the outset some hadn’t even heard of trade unions. Oh, and let’s not forget that they were all women – which in our jobs market makes you much more likely to be on crap wages. Game, you might say, over.

School dinner ladies in Camden are receiving a pay rise of £2.55 per hour. Photograph: Graeme Robertson/The Guardian

Except one thing really annoyed Camden’s dinner ladies: they knew that Caterlink also provided school meals to Islington, the borough next door, and that the council there had insisted all staff get London living wage. Which meant that in schools just a few minutes’ walk away, women doing the same jobs were earning hundreds, thousands more.

This is where things get even more interesting – as the impossible slowly became first achievable, then a done deal. Barnes went to the library, began reading up on workplace rights and ended up joining a union. The women’s campaign for better pay cranked into gear late in 2013, and over the next year and a bit the number of dinner ladies signing up with Unison climbed from fewer than 25 to well over 100. This was the outcome of hundreds of face-to-face conversations with dinner ladies across the borough, some of whom took convincing that union activism would not jeopardise their jobs (for the record, no one I’ve spoken to has said Caterlink managers attempted to dissuade the women from joining a union – but the fear was still there). Four of them ended up taking a week’s training in how to become shop stewards.

In dealing with the union, Caterlink argued that the contract didn’t allow it to pay the London living wage. Yet at the same time its parent company, Westbury Street Holdings, was buying champagne bars for a reported £25m-£30m. This is where two other elements become very important. First, the local newspaper, Camden New Journal, began campaigning hard for the dinner ladies – including sending a reporter and snapper to the Berkshire mansion of Westbury’s chairman and chief executive for a classic bit of name-and-shame. Each story dented the reputation of Caterlink, which is trying to grow its school-dinner business across the UK. Second, the Labour-run Camden council had made a big deal of campaigning for equality.

By early spring of this year, the dinner ladies had won concessions but not the immediate grant of a living wage. Then came a rally at the Town Hall, at which the staff first banged pots and pans then told councillors how they served roast beef to schoolchildren while feeding their own kids jacket potatoes. With the general election imminent, the council and Caterlink agreed to the demands. The dinner ladies won.

You might at first think this story heartening – but unique. After all, how many other Annie-Roses are going to sit in a reference library? How many other union branches will try a bit of direct action, or local freesheets be willing to annoy the council that give them so much advertising?

Yet the more I turn it over, the more I think this tale tells us something bigger: that what we’re told is political and economic common sense can be shown up as nonsense. We’ve grown used to compromises and accommodations, to accepting whatever’s deemed realistic, even if it’s useless – whether that be bad wages or an opposition party with a permanent cringe. And then 300 women get it together and show that it needn’t be so.

So Camden dinner ladies deliver the first lesson of the academic year: crap jobs can be made better. And the very act of refusing what’s doled out to you can work wonders. Barnes has just moved from her old school job, but plans on getting involved in organising her new workplace. “I’ve already got my eye on a couple of new campaigns,” she says, and cracks up laughing.