The Sturm und Drang of the world’s biggest theatre show

The Flemish call it Veertien- Achttien and describe it, in the lilt familiar from the subtitled television series Salamander, as a spektakel musical. To the rest of us it's the world's biggest theatre show.

Everything about 14-18 is enormous. The musical is being staged in a specially adapted building that could happily house a decent airport. It's running for a year. It has a cast of 140. The set is made up of 11 gigantic pieces of computer-controlled kit that can represent, with a graceful turn and a change of lighting, a bridge, a village green and a ruined city.

All of which might lead you to suspect that if you travel to the pretty Flanders town of Mechelen, a 10-minute train ride from Brussels, to see 14-18, you can give up on the idea of theatrical immediacy or intimate storytelling. In fact the opposite is the case. The show takes its audience to the centre of the action on a 2,000-strong chunk of seating that moves backwards and forwards along a 15m track.

The sensation is uncanny. Your brain is telling you that you're watching a cinema panning shot, but your body knows that it's you doing the panning. The pace is stately. It's not a fairground ride. But it's not a gimmick, either. Or rather, it is a gimmick, but it works. There you are, sailing into the middle of a series of explosions, or towards a line of armed soldiers who are walking towards you, firing as they come. Real trucks clatter across the stage. Real horses canter right and left. With 14-18 you don't just get the illusion of 3D action. You're in the middle of it and can't get off.

Which is exactly what happens to the characters in the story: Jan and Kamiel, who are brothers, and their young friends Fons and Albert, who become enmeshed in the murderous mess of the first World War. Through flashbacks we learn that Kamiel wants to be a musician. Fons is a bookworm, Albert a ladies man. When Jan goes to fight he leaves behind his pregnant wife, Anna.

“We follow four friends, each of whom has a small story in the big story of the war,” says Tijl Dauwe, the show’s assistant director. “You follow people in those four horrible years, and you see the changes in their characters and how they cope with the madness.”

Dauwe and his colleagues from the production company Studio 100 worked with academics from the Ypres museums on 14-18's historical accuracy. There are school performances for children aged 10 and over; such has been the demand that there is a waiting list for tickets.

“It’s an important piece of history for Belgium, and we have to pass it on to the children. They have to know what happened,” says Free Souffriau, who plays Anna. Dauwe agrees. “It’s kind of a forgotten war, you know?” he says. “Here in Belgium we all have grandparents who survived the second World War. But the first . . . well. At school you go to museums and memorial sites, but you don’t really know how it felt to be living through this terrible time.”

Giant’s toyshop

Before the show begins we’re given a tour around the cavernous backstage area at the Mechelen Nekkerhal. It’s like a toyshop for a mad retro giant. We pass racks of guns, a pair of hospital beds, several bicycles, a chandelier and a vintage jeep with a mud-splashed windscreen. Hanging in immaculate rows are 350 numbered costumes. A wooden cart contains a small, fuzzy white body. I have a sneaky feel through the rough bars; it’s soft and feathery. A pretend chicken.

Make-believe it may be, but the technical challenges are all too real. The sound system for 14-18 has to travel seamlessly back and forth with the audience. The lighting had to suggest everything from a jaunty village wedding scene to the jaw-dropping moment when a set of floodgates open and a tsunami of rippling "water" flows across the floor towards our seats. (It's an illusion, but it's all I can do not to snatch up my feet.)

For the cast – the cream of Belgium's young singer-actors – what has been the biggest difficulty of playing in a production on this scale? "Techniek," says Free Soffriau, with a rueful shake of her red head. "It was a bit difficult in the beginning . . . We all, all the actors, have our own track to move along, and you have to follow it exactly. You don't mess with it – or the tower will kill you."

We laugh. But she’s not joking. Each piece of scenery, controlled wirelessly by a kind of automated GPS system, moves autonomously along tracks at either side of the stage, an area known to cast and crew as Death Alley. It has implications for the audience, too. It means that once you get into your seat, that’s where you stay. There’s no interval – too emotionally disruptive, decided Frank Van Laecke, the show’s director – and there are no toilet breaks. Queue for the loo before the show starts, or you’ll live to regret it. And too bad if you’ve overindulged in Belgian craft beer at the foyer restaurant earlier in the evening.

None of these strictures appears to bother the capacity audience, which is on its feet for a standing ovation at the end of the night. What's the world's largest theatre show like? I see it in Flemish – and it is still spellbinding. Having seen the fabulous War Horse in Dublin a few days earlier, I don't expect to be blown away again. But I am.

The big battle scenes of 14-18 alternate with conversational vignettes to ensure that there's never a dull moment. Dirk Brossé's score shifts easily from symphonic vastness to well-crafted pop melodies; small wonder that he was nominated for an Emmy for his score for the BBC series Parade's End, with Benedict Cumberbatch.

Cheese alert

Certainly there are moments – when Jan, played by Jelle Cleymans, sneaks across the devastated landscape to meet his three-year-old son for the first time, for instance, or when a German soldier holds out a hand to shake that of his opponent while a voice sings

Silent Night

and snow begins to fall – when you know you ought to be on high cheese alert. Except that you’re too busy rooting around for a tissue. And the end – no spoilers, but this is the first World War, so don’t expect happy ever after – has dignity and beauty.

The English actors Danny Whitehead and Kayleigh McKnight are being trained to play Jan and Anna in an English-language performance on June 15th. If it’s a success there will be more, making the piece accessible to a new audience.

If ticket sales hold steady over the next 11 months Studio 100 will make its money back. But the project is not, Tijl Dauwe says, just about money. “There’s a fine line between the integrity of the show and commercial considerations,” he says. “But the respect is important. It’s the most important thing.”

You can find out more at 1418.nu/en