Mike Leigh's 'Peterloo' Is the Important History Lesson You Never Had

More than 700,000 people turned out to march about Brexit in London last month. All were aggrieved by a sense of blatant political injustice. All marched in peace and safety. This freedom to protest unmolested is seen as standard in the UK these days, but it hasn't always been the case.

In Peterloo, the new film by Mike Leigh, the director gives us a deep dive into frighteningly recent history and reminds us that, when it comes to suffering social injustice, it's all relative; that when it comes to personal security, marchers haven't always been so lucky.

The true story of Peterloo is a sobering one. On the 16th of August, 1819, four years after the English triumph on the battlefield of Waterloo, 60,000 people walked to St Peter's Field in Manchester. Their issue with political leaders was manifold. High taxation, bread prices and prohibitively expensive corn had left an entire class scratching for survival while the elite few enjoyed the fruits of the industrial revolution. Meanwhile, representation was so skewed that even a city the size and significance of Manchester lacked its own MP. Reformers were holding meetings nationwide where the mood ranged from mild to militant.

The country was hungry, angry and ripe for revolution, just like the French before us – exactly what the establishment most feared. Hence their reaction to the protest that day when they set the troops on their own people, killing at least 15 and injuring hundreds more.

It's not a widely shared or taught story. Mike Leigh himself went to school a 15-minute bus ride from the site of the massacre, yet as he recently told the Guardian, this brutal chapter barely made it to his classroom blackboard. "We did it for four seconds for O-level," he remembered.

Half a century later, it's taken Leigh's own significant effort to right this educational wrong with his most ambitious and political project yet. His 154-minute epic, three-and-a-half years in the making and boasting a 160-strong cast list, retells the catastrophic string of events that led this country from the triumph of Waterloo to the tragedy of St Peter's Field, Manchester, hence "Peterloo" – the bitterly ironic name given to the latter on the day by a Times reporter and witness.

It's no surprise to learn that in the years between the two events people were just as angry as they are now. Mutterings in pubs echoed the zealous shouts of Reformers on hustings, all asking the same question: what good is a government that doesn't serve its people? Sounds familiar. But despite our present-day troubles and arguments about what constitutes actual democracy – not least the intricacies of a genuine people's vote – it's worth remembering that at the time of this film's events, less than 3 percent of our population had any right to vote at all.

It's a huge canvas of a tale, but Leigh's eye is all-seeing and unsparing. He brings us the plight of a thousand families in the dynamics of one, whose son Joseph we meet in the opening scene on the battlefield of Waterloo. Still in his red uniform jacket of English military victory, shell-shocked and empty, he makes his long way home to his family in Manchester, where he gets nothing from his country in return for his effort. These days, Joseph's treatment alone would make a decent film. Maxine Peake is on fire as matriarch Nellie – the actress has revealed she wrote to Mike Leigh, asking to be involved as soon as she knew Peterloo was on his radar – and her commitment shines through every scene, even as she goes about trading home-made pies for eggs and hoping for better days.

Local magistrates (Bodyguard’s Vincent Franklin, Grantchester's trembling curate Al Weaver) charged with preserving the status quo and quashing any intimations of rebellion are also clergymen, but delight in banging their gavels and meting out capricious courtroom punishment. It would be comical if it wasn't all so historically, horribly accurate. One convict is despatched to Australia for nabbing a pocket watch. He got lucky – another is sentenced to hang for stealing a coat.

If these legislators appear exaggerated in their loucheness, the Prince Regent (Tim McInnerney) is outright grotesque, bulbous and self-adoring, to the extent that some critics have accused this portrayal of caricature. But Mike Leigh has done his homework – those rouged Regent cheeks were as real as the Prince's vile indifference to the plight of his citizens. Nobody's perfect in this story. As with all political struggles, vanity and piety reveal themselves in many quarters. Actor Rory Kinnear perfectly depicts the Orator for the Reformers, Henry Hunt, and his superior manner and tight-lipped contempt as he arrives in Manchester and is forced to take lodgings with a local newspaper owner.

But even as Leigh lets us enjoy this elbow-bumping for power on both sides – the magistrates bickering about who gets to be chairman, Reformers arguing about who gets to stand where on the hustings – the director makes no bones about where his real sympathies lie.

The moral high ground belongs to those workers who dressed in their Sunday best, put children on shoulders and set off that Monday morning to take their place in St Peter's Field – intent simply on peaceful protest and having their voices heard.

Even without knowing the history, even as Henry Hunt orders his protesting supporters to go in un-armed, as a magistrate's shouted order to disperse goes unheard, there's a crushing sense of inevitability about the whole thing – but the final 30 minutes of the film are no less shocking for it. Three camera crews catch the mood, moving from optimism, to chaos, to terror and finally despair, every flash of blade, every wife's cry, even a moving glimpse of Joseph, still in that red uniform souvenir of England's finest day.

The battle scene – there really is no other word for it – is a fitting bloody climax after two hours of reforming zeal and shameless establishment chicanery. Even so, no less moving are some of the moments of reflection shared by some of the gentler characters. As Nellie watches over her sleeping child, she reflects that, in 1900, "she'll be 85, I hope it's a better world for her". Her husband's response? "Some things'll be better, some things never change."

Mike Leigh's 'Peterloo' is in cinemas now.