"So you're not with all the fashionable people, then?" someone remarked to me after Sunday night's rehearsed reading of Serjeant Musgrave's Dance at London's Royal Court. By that he meant that I wasn't with the glitterati at the Evening Standard theatre awards at the Savoy Hotel. Not for the first time, I was delighted to be deeply unfashionable. The reading of Serjeant Musgrave, mounted as a tribute to playwright John Arden, who died in March this year, was a shattering event with significant lessons for the future.

The first thing it taught me was the positive power of the rehearsed reading. Director Peter Gill had assembled a top-notch cast for the reading of Arden's play, originally seen at the Court in 1959. Among the 16 actors and one musician on stage were Brendan Coyle (John Bates in Downton Abbey), James McArdle (from Chariots of Fire), Sarah Lancashire, Philip Jackson, Clive Merrison and John Savident. Over the course of two days' rehearsal, they had come up with a brilliantly clear account of Arden's play. And while I've no wish to see this as a barrier to a full-scale revival, it struck me as important for the future. I'd love to see Vicky Featherstone, when she takes over at the Court in March, making Sunday-night readings a monthly event. It's an excellent way of reminding us of plays that, whether because of cast-size or scenic demands, are all too rarely seen.

The work of John Arden deserves attention. As his widow, Margaretta D'Arcy, pointed out to me, his plays were often astonishingly prophetic: she cited The Happy Haven, which deals with our often heartless treatment of the elderly. And Serjeant Musgrave's Dance seems horrifically topical at a time when stories of retaliatory abuse by British troops in Afghanistan and Iraq are gradually coming to light. In Arden's play, the titular hero and three fellow-deserters seek to import to a strike-bound northern town the violence in which they have been complicit in a Victorian colonial war. Coyle was magnificent in suggesting that Musgrave's motivation lay in a profound religious sense. At the same time he indicated the madness in Musgrave's method with its brutally logical notion of revenge.

It's a great play precisely because we feel so ambivalent about Arden's hero. But the work also possesses a linguistic richness of which we are sadly starved in modern British drama. Arden, like Shakespeare, has a spendthrift generosity that enables him to give memorable lines to even supposedly minor characters: at one point Annie, who works in the local pub, admonishes a deserting redcoat with: "Every one of you swaggering lobsters, that serjeant squats in your gobs like an old wife stuck in a fireplace." Annie, like the other characters, also moves effortlessly from sinewy prose into sung verse in a way that makes words dance.

I came away from the Court yearning for a rebirth of prose-poetry on the British stage, and convinced that, in straitened times, the rehearsed reading is a way of keeping our theatrical inheritance alive. The fashionable may have flocked to the Savoy on Sunday, but I swear the really momentous event was taking place on the stage of the Royal Court.