It is the stuff of campaigners’ dreams and Hollywood endings. One day you are fighting to right a great wrong but it seems no-one is listening. Within a week millions have rallied to your cause, the media are clamouring for interviews, and the Prime Minister is being pressed on what he’s going to do about it.

That is the position victims of the Horizon IT scandal find themselves in after ITV’s screening of Mr Bates vs the Post Office last week. A fight that has been going on for more than 20 years rocket-boosted by four hours of primetime drama. How did that happen?

Gwyneth Hughes’s drama (available on STV Player) set out how hundreds of sub-postmasters across the UK had reported problems with the Post Office’s new computerised accounting system. Instead of listening, the state-owned business turned on them and wrongly accused them of theft. People were jailed, lost jobs, homes, reputations and their health. Some took their own lives.

The Herald:

It has been called the most widespread miscarriage of justice in recent times and it is far from over. Over the weekend the Metropolitan Police confirmed it was investigating complaints. A petition to strip Post Office boss Paula Vennells of her CBE is heading for one million signatures.

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The focus is now turning to why more was not done by ministers at the time. Included in their ranks are Ed Davey, then postal affairs minister, now Liberal Democrat leader, and Jo Swinson, former MP for East Dunbartonshire.

It was clear from early on that Mr Bates vs the Post Office had touched a nerve. In these days of working from home people don’t gather around watercoolers any more to talk about last night’s TV (if they ever did). They go on social media instead. This time, some went old school and spoke about the drama with strangers in shops and cafes. It was the talk of the queue in my local Post Office.

Such is the power of drama when pressed into the service of a cause. Think of Cathy Come Home (1966), a searing exposure of homelessness.

Boys from the Blackstuff (1982) took on the new Tory government over unemployment. The BFI called Alan Bleasdale’s drama “a warm, humorous but ultimately tragic look at the way economics affect ordinary people” and “TV’s most complete dramatic response to the Thatcher era”. (Let us not forget it was also home to the best Desperate Dan joke ever made.) How much support for Scottish independence came from a night at the theatre, or in front of the television, watching John McGrath’s The Cheviot, the Stag, and the Black, Black Oil?

How many had their worst fears confirmed about the war in Iraq by Gregory Burke’s Black Watch?

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How many young women found feminism (and Margaret Atwood) through Channel 4’s adaptation of The Handmaid’s Tale?

House of Cards, Yes Minister, The Thick of It, The Good Wife … to misquote a certain advertisement, all have been able to reach the parts conventional politics, and the coverage of it, has failed to reach. Even the seemingly lighter takes, such as The Full Monty, with the late Tom Wilkinson as an unemployed steelworker turned stripper, have packed a punch way beyond that of any speech in parliament.

Little wonder other campaigners are looking at the “Mr Bates vs the Post Office” effect with envy. But the first thing to note is that such a reaction happens rarely. Most dramas will steer clear of anything too political for fear of turning off viewers.

The Herald:

There is more chance of a soap picking up a subject and running with it. At the moment, Coronation Street has a character with motor neurone disease, Paul Foreman (played by Peter Ash). The writers have worked closely with the Motor Neurone Disease Association and others to make the portrayal as accurate as possible.

On its website the MND Association says it is grateful for the time and effort spent by the scriptwriters and production team on getting things right. “Coronation Street is a drama and there has to be a certain amount of artistic license. From what we've seen so far we are confident that our community will recognise conversations, situations, challenges and solutions they themselves have faced.”

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The “artistic licence” point is important. Every drama that bills itself as a true story, or based on/inspired by a true story, will come with caveats. Mr Bates had the standard “some names and characters have been changed, some scenes imagined”.

So far, makers Little Gem and ITV Studios have been praised for their accuracy. There really were convoys of PO investigators in suits swooping to tell subpostmasters they were being investigated. Children were bullied at school.

Where the ITV drama excelled was in making the political personal. Having a handful of main characters ensured that viewers cared what happened to them. Reading about a person’s breakdown is one thing, as is hearing them talk about it later. But to “be there” with them at their lowest point, only drama can do that.

Making a drama out of a true story comes with risks as well as rewards. Inaccuracies, or scenarios that are too far fetched, can leave a production open to criticism. The Monocled Mutineer, for example, was first attacked by historians when it aired in 1986. This left the door open for the tabloids and Tory MPs who disliked the drama’s working-class hero, and the BBC in general, to pile in.

Even if a drama does catch the public’s attention there is no guarantee how long the focus will last. The Horizon story broke in Computer Weekly and Private Eye around 2009. Every now and again it would be picked up by other journalists, but nothing cut through like ITV’s drama. Was the story deemed too messy, too complicated to tackle? How many other scandals are out there, deserving of the Mr Bates treatment but who will not get it?

Only 93 of the 700-plus wrongful convictions have been overturned. Many are still waiting for compensation and a personal apology. It could be years yet before this story concludes, and no guarantee that justice will be done.

But in the meantime, all hail the box in the corner, and the flat screen on the wall, for a first-class job.