Film history is rife with successful transfers from the stage, from Best Picture winners like Olivier’s Hamlet (1948), Oliver! (1968), and Amadeus (1984), to no less worthy ungarlanded classics such as Kazan’s Streetcar Named Desire (1951) and 12 Angry Men (1957). Recent adaptations like Rabbit Hole (2010) and Doubt (2008) testify to theatre’s vitality as a source for films. Texts travelling in the other direction, on the other hand, are much, much rarer. Why?

Part of the answer is simply mathematical: theatre is vastly smaller than film. The UK’s annual theatrical box office approaches something like £500 million, generously including musicals and concerts, or £80 million for plays alone. Last year in the UK The Last Jedi and Beauty and the Beast each took more than £70 million, and films as a whole grossed well over £1300 million.

But some of the asymmetry comes from the intrinsic constraints of the forms. In film a scene change is as light as a cut: filmmakers are incentivised to exploit shorter, more numerous scenes spread across more locations. Theatre is clumsier and so likely to concentrate its action. Even a relatively mobile play like Frost/Nixon barely tops 20 scenes, while the average two-hour screenplay spans 60 or so. Films are at liberty to show us the things theatre can only gesture at – chases, races, mountains, crowds – and so depend less heavily on dialogue. And while it’s usually a short cognitive step to flesh out an abstracted stage-world into corresponding reality, the journey vice versa is much less intuitive. It requires deciding not only which elements are worth keeping but also how – a question tightly bound up with the material’s texture and tone, and much more more complicated and important than it might initially seem.

I hadn’t really thought about all this when I applied to adapt The Seventh Seal (1957) for the stage. I knew the film was based on a play and that, although the world remembers Ingmar Bergman, its Swedish writer-director, for his rich filmography, he got his start in the theatre and worked there primarily for most of his life. In some ways it turned out to be a difficult text to adapt, in others more easy.

Its dialogue is whimsically understated, and it has been accused of inaccuracy in its imagined medieval Sweden: Roger Ebert rightly suggested “The Seventh Seal has more in common with the silent film than with the modern films that followed it”. It also moved him to an uncharacteristic broadside against contemporary cinema’s commitment to “facile psychology and realistic behaviour”. The line misrepresents the brilliance with which Bergman directed actors, but its backward compliment to the film’s existential heft and thematic unity is apt. It’s symptomatic of the scale of the admiration The Seventh Seal inspires that one of the most persuasive champions of mainstream cinema’s ordinariness saw it and, for a second, seemed to change his mind.

A great part of the film’s appeal derives from its infectious audacity. It begins with, and is constructed around, one of cinema’s indelible images: a knight playing a game of chess with Death. That conceit contains already, and in the right ratios, the absurd playfulness about seriousness that its parodists – most famously Monty Python in The Meaning of Life – exaggerate; in assigning the film a ponderous symbolism to be punctured, they’re missing the point. Although our adaptation brings an affectionately parodic verve to some scenes (we allude among others to Monty Python) the wit at its core is Bergman’s own. To watch the film today is to feel its vitality, its still-intact humour, and the brilliant idiosyncrasy of its writing.

In other ways the film has aged less well. If anything its sexual politics are progressive for its time, but it contains too many thinly-drawn women to overlook, and some uncomfortable scenes. We cast Hannah Lyall as the Knight chiefly because of her terrific audition, but also because even today the vast majority of plays are needlessly male-led. Paul Clarke (our Death) doubles as a comically inadequate Lisa – whose main characteristic is loving men, inconstantly. Dozens of smaller decisions and alterations were intended to redress its complex but unmistakable biases.

The camera’s freedom to deconstruct and rebuild has no equivalent in theatre: this is why staged film is likely to feel incomplete. Even if theatre could recapture film acting’s precision (because cameras can capture behaviour on any scale) and accuracy (because of freedom with takes), and it certainly can’t, the question would remain: what justifies the adaptation? I saw the Chariots of Fire musical a few years ago, and Aladdin more recently. Both, though enjoyable, felt unserious compared to the originals – deft stokers of nostalgia, undeniably, like Trainspotting 2, but also, like that film, finally superfluous.

What we’ve added in The Seventh Seal, roughly, is an Emma Rice-inspired irreverence about representation – mannequins, a puppet, projection, and mime – and also Rice’s deft mobilisation of anachronistic contemporaneity. Instead of a procession of monks carrying censers and a life-size Jesus on the cross, trailed by half-crazed flagellants, we have a street evangelist. Lorena Paton, our costume designer has devised a highly creative way to represent the burning of the ‘witch’ – you’ll have to come along to see! Our costumes reproduce medieval motifs in 21st-century ways, and our performing troupe play music by beloved rock and roll bands.

Music, as ubiquitous in film as theatre, translates well in both directions. Live performance lends it a unique intensity and inclusivity – we share, somehow, in the music performed in our presence, while filming permits an exactitude of rendition and synchronisation. We didn’t add much dance or spectacle, nor does our play depend on the pleasure of seeing technical solutions realised in real time, but there is song and, in lighting and projection, some visual beauty of a uniquely theatrical kind.

We left many things unchanged. The theme of God’s muteness, characteristic of so much of Bergman’s work, is there intact, and the film’s indignant anti-clericalism too. While the Knight’s journey is inextricable from faith, I don’t think The Seventh Seal’s central subject is religion so much as companionship and suffering – part of why it interests a committed atheist like me. We all die alone, of course, it says. But it’s better to do that with friends.

The Seventh Seal is on at the ADC Theatre 7-10 February