This writer will leave it to historians to comment on the details of the causes and facts of the massacre at Peterloo on 16 August 1819. Mike Leigh as writer and director doesn’t leave that much to the imagination or doubt as to the institutions responsible to the general viewer. From the Prince Regent down to the magistrates to the yeomen its painted in clear strokes.

They are not broad mind as there are details in the state’s power and machinations. The magistrates in particular held incredible power seeming to dispense justice almost without referral to the law. There’s General Byng (Alastair Mackenzie) drafted in by a scheming Home Secretary and totally impartial private secretary, to keep the peace in the north, decides he has better things to do the day of the gathering.

The film opens young Joseph (David Moorst) a bugler in Wellington’s army making his way home from Waterloo, clearly traumatised, to Manchester. He’s greeted by his mother and family and to news that salaries are being cut and thanks to the Corn Laws basic food stuffs are proving to be almost beyond their reach. This and other factors are playing into the radicals’ ideas of one man one vote at mass meetings. There’s a mood for change but attacks on the king and an institutional paranoia is such that citizens’ rights are suspended.

Weaving together the state, the radicals and the people Leigh builds the background of the massacre amidst sumptuous sets and a colourful script performed by some to UK’s leading actors. It’s rich in description from the beautiful scenery to the mind-numbing noise of the mills. There’s also vast amount of people involved with new minor or major characters folded in regularly. They don’t compete for space but one wonders if some judicious pruning would really have damaged the fundamentals of the story.

It’s as we draw towards the massacre itself that matters develop with the magistrates ordering the arrest of leading radicals, and then in a meeting with Henry Hunt who is there to address the crowd where they agree not to arrest him. Hunt (Rory Kinnear) is a curious character in that he is clearly wealthy and has no need to trumpet any reforms. He also has a massive ego with the oratory skills to match and there’s a sense that he may not be truly sincere about the causes he advocates. He is eventually arrested as the magistrates get their way, calling on the yeomanry to tackle the crowds with devastating results.

Kinnear’s performance is supple as Hunt deals with the various factions with slippery assertion. With considerably less time on screen he’s matched by Tim McInnerny’s grotesque fop of a Prince Regent. But it’s the magistrates – and the four that the film concentrates on Messrs Ethelston, Hay, Fletcher and Norris (brilliantly played by Vincent Franklin, Jeff Rawle, Philip Whitchurch and Martin Savage respectively – that stand out as the rotten core. Clad in black they are truly ugly and malevolent; caricatures of Gillrayan proportions.

At two and half-hours it’s a long film and there’s a steady pace towards the fateful day but it does feel cluttered at times as there are a lot of speeches that don’t always sit comfortably within the overall narrative. The attack itself is graphic but not gratuitous and Leigh convincingly conveys the terror and confusion of the people on that day.

There’s plenty in Peterloo for people to chew over and debate how the event may relate to today’s politics. However, the essential thing is that the story of this little known but important part of this country’s history has been told.