Why do puppets work? They don’t look real, like actors, and the strings are always visible. Somehow a true puppet master can steer us past that. Within, sometimes, seconds, the artifice is forgotten and our emotions are engaged. This is something to do with the poignancy of the way the puppet is almost, but not really, alive. “The puppet is an object that struggles to imitate what human or animal life is really like,” says the puppet master Adrian Kohler. “It triggers the audience’s imagination in a much more fundamental way than an actor does, because they have to will it into life, much as the manipulator does.”

So, perversely, it is the artifice, the all too visible contrivance, that makes puppets poignantly real to us. They remind us how awkward, contrived and artificial we seem to ourselves; we empathise with their plight because we, too, are pulled this way and that by some invisible hand. Kohler’s colleague Basil Jones extends the point. “They replicate our daily struggle, just getting out of bed or going to that meeting, all those small events in our daily lives that are silly in a way, but nevertheless we identify them as being difficult. You identify with all those things when you see a puppet.”

Kohler and Jones are on the phone from South Africa. They are the founders of the Handspring Puppet Company, based in Cape Town, and know all there is to know about the puppet struggle. I can say this because I have just seen War Horse at the National Theatre, for which Handspring did the puppetry. The star of the show is Joey, a horse — or, rather, a cane frame operated by three men. We first meet Joey as a foal, another cane frame, then, in a coup de théâtre that makes everybody gasp, he turns into a full-grown horse. Joey rears three times; the third time, his operators swerve away, each carrying a part of the puppet into darkness. It’s as if he has evaporated.

A rearing big Joey then appears, as if out of nowhere. The effect of this coup is to dispel any remnants of audience refusal to accept the life of the puppets.

After that, there is no question that Joey is a horse. Schoolgirls, therefore, love him. The night I went, when the show ended, rows of them started screaming; some appeared to be close to passing out. It happens, apparently, at every performance. And often it’s not only the schoolgirls. “Perhaps there’s a schoolgirl in all of us,” grins Tom Morris, the production’s co-director (with Marianne Elliott).

War Horse is a National Theatre oddity. When Nicholas Hytner took over as NT director in 2003, one of the first hits was an adaptation of Philip Pullman’s His Dark Materials trilogy. He wanted to build on this success and was on the lookout for material that would, like the Pullman, attract a crossover teen/adult audience. Morris started reading and alighted on the works of Michael Morpurgo and, specifically, his War Horse. It worked triumphantly, and the show is now transferring to the New London Theatre, in the West End. Advance bookings are well above £1m.

The show is the story of Joey’s experience of the first world war. Why that war, I ask its author?

“It seemed to be the last of the great imperial wars,” Morpurgo says, “and in the midst of it all was this appalling suffering wreaked upon ordinary people. The animals were part of that, some of the millions of victims of man’s extraordinary desire for power.”

It was the last war in which horses played a significant combat role. This was absurd. A single machinegun could mow down a cavalry detachment in its tracks. Yet the imperial armies doggedly clung onto their horses. As a result, one of the many horrors remembered by veterans of that war was the sound of wounded and distressed horses as they slithered to their death in waterlogged shell craters. What made it so awful was the innocence of the horses. From Black Beauty to Picasso’s Guernica, the horse has been a symbol for innocence, honesty, a creature capable of a deep connection with human beings. “The horse comes with this baggage,” Morpurgo says. “It comes with great beauty, nobility, sensitivity and its association with man.”

“They are honest,” echoes Morris, “and people who work with them say they are honest. They don’t bullshit.”

The horse is on the side of humans in general, but not of our particular tribal causes. Joey, with another puppet horse called Topthorn, crosses lines and becomes, for a while, a German horse. This is the power, for Morpurgo, of the horse as hero. It is a neutral, innocent, loving observer of our follies.

“One of the great problems about stories of war is that you necessarily take one side or another. But I don’t think there’s any way you can tell the story of this war other than through a neutral observer. The horse made me able to tell the story from all sides, but it’s also a tool that makes it much more likely that young people will allow themselves to be drawn into a historical subject — and most of them don’t know about the first world war. I think that’s the reason, really: it allowed me to draw myself into the story, and children as well.”

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