WHAT a wonderful way this is to do theatre: play your scene, pile everything on your wagon, gather your minstrels, and trundle off through the crowds and sunshine to the next location, where you'll do it all over again. And again. And again.

There's no amplification, no technical support of any kind. The audience includes the dedicated, the curious, and the incurious. Dogs lie on the grass in front of the seated area in Dean's Park, where painted devils snatch a drink from a vintage tea-van before it all starts. The York Mystery Plays can't be bettered, as much for the pageant of life which goes on around them as for the power of the plays themselves.

And powerful stuff it is: a rich and exhilarating tapestry of styles and interpretation of the medieval texts. York Guilds and Companies are the guardians of the tradition: the robust, alliterative language comes from the mouths of players from churches, schools, universities, and performance groups of every kind, with a passion that moves and a freshness that delights. Early music on myriad period instruments prefaces, infuses, and interprets the plays; the minstrels are a pageant in themselves.

The 12 texts here are a mere fragment of the original 48, andtake almost four hours to perform. It is a tough trajectory from The Creation of the World to The Last Judgement: from the comedy of God as a 14th-century master mason who can't start work until he's had a cup of tea to the crowned and angry Christ at the end of time, golden among the science of clocks and cogs.

There are pockets of relief in the later story - The Entry into Jerusalem is an Edwardian, pre-war summer day, where whole households are on the street to enjoy the fiddle-playing and witness the healing of the cripple, and where Jesus can freely roam into a receptive audience.

But the comedy really stops after The Fall of Man (impishly played out by three teenagers from Canon Lee School) and The Angels and Shepherds. Their carnival-winged angelic hosts sing "In the bleak midwinter", and the shepherds feign astonishment at the bobbing star on its bendy pole. We needed the laughs because now we are plunged into The Massacre of the Innocents, where storm troopers with Kalashnikovs bayonet babes-in-arms, a black-shirted Herod puts a pistol to the messenger's head, and the Vicar of Heslington (whose congregation are the players of this scene) is felled as he tries to intervene.

Two of the most powerful episodes are performed by staff and students of York St John University. The persecutors of The Woman taken in Adultery are mouthy ladettes in caps and weskits; the mass wailing and the orchestrated, head-clasping lament of the women in The Raising of Lazarus strikes a familiar chord with daily TV footage from the Middle East. There is no wistfulness in the accusation of Jesus: their charge, "If only you had been there!" is screamed with rage.

A female Annas outside a grubby courthouse, with a wise and composed young Jesus hooded and kicked in turn by two cadets, leads into The Crucifixion and The Death of Christ.

Part of the fascination of seeing the plays done in the pageant-wagon way is that there's no concealment, no backstage preparation. It is poignant to watch the careful pre-placement of the red silk ribbons that will be the flowing blood from the Cross.

And watching Jesus at the hands of a sadistic sergeant-major and callous, beer-drinking soldiers cuts to the quick. This is a searing performance from John Hoyland as Christ. His straining ribcage and animal cries still the audience. His cry, "On rood I am ragged and rent!" rings across York. His family stamp in concerted agitation as death reaches its climax. It is the young soldier, not a thief, who asks forgiveness and is promised paradise, and the episode concludes with a pipe lament and the sung words of John Donne's poem "Death, be not proud".

I watch The Harrowing of Hell twice - once from the seating of Dean's Park, and once among the shoppers and tourists in St Sampson's Square. To happen upon the plays, glimpsing just a fragment of the story as many do, brushing with story and history, is a baffling and elusive and marvellous thing. The crazy urban wasteland of hell with its junk and rubble, its barbed wire, its steely girl Satan, and its collection of waiting souls looks even grimmer with Pizza Express in the background rather than the gracious buildings of Dean's Park.

As an audience, we are taughtby the expository Chorus of three- a new narrative strand to the plays - to sing Resurgens "with a rising sense of joy" in preparation for the Resurrection. A feisty bunch of Yorkshire housewives are the guards, bribed to spread false rumours. But the best in theatrical terms is still to come: a surreal and terrifying Last Judgement with a steampunk morris band in black basques and goggles and the black and white flowers of damnation and salvation randomly distributed in the audience. Through no medium is the story better told.