It's not a line I recall from the 1939 film of Gone With the Wind, but we're told something really startling about Scarlett O’Hara at the start of the second interminable act of Margaret Martin’s new musical play: “She walked every day for miles looking for yams.”

Frankly, my dears, I don’t give a yam, but there's a bizarre suggestion in Trevor Nunn’s production that Scarlett morphs into some kind of Mother Courage of the American Civil War, pulling her baby and belongings around on a gun carriage after the burning of Atlanta before breaking into a hymn to the transforming powers of flatulence: “The life I used to know has gone, gone with the wind.” No more curried eggs for her, then.

Jill Paice as Scarlett gives everything she’s got to this item, which I cannot label as the programme does not list musical numbers. These numbers, anyway, don't stand alone, but sidle out of the show with their footling orchestrations like guilty little secrets. If only they’d remained so. One exception is a rousing anthem to freedom by a chorus of black slaves left over from Nunn’s recent sub-standard Porgy and Bess.

The productions by Nunn and John Caird of Nicholas Nickleby and then Les Miserables were two of the greatest in our theatre of 20 years ago. They were rooted in the RSC company ideal and expressed stories of epic scale and panoramic detail in a passionate stage language that summarised other early 1980s experiments in narrative theatre and, in the case of Les Miserables, found a soaring, modern Verdian musical style to match.

Here, the distribution of the story among scattered third person parties around the huge plantation verandah design of John Napier seems like a solution to a problem, not the result of any urgency in communication. Once inside the unfriendly New London, the arena, you have to admit, is thrilling. As in his King Lear and The Seagull for the RSC last year, Nunn knows exactly how to exploit this space to the full, arranging the company hoe-downs and cakewalks with real flair, much flattered by the wonderful array of crinolines, gingham skirts and frock coats by costume designer Andreane Neofitou. The burning of Atlanta, lit by Neil Austin, is an orange glow in an ever-changing sky.

Jill Paice runs a gamut of emotions from A to B, as Dorothy Parker once said of Tallulah Bankhead, but she does so with endearing charm. There's a collective intake of breath at the sight of “Pop Idol” Darius Danesh as Rhett Butler; he’s about seven feet tall and blessed with an extraordinary bass baritone voice that he may find a way of using properly one day. For now, oddly stiff and smarmy at the same time, he looks like a joke entrant in a Clark Gable lookalike contest.

Nunn has bolstered his company with such reliable performers as Susan Tracy, Susan Jane Tanner, Jeff Shankley and Ray Shell, but none of them has much chance to shine in the encroaching, deadly mediocrity of the material. Edward Baker-Duly has a fair stab at Scarlett’s beloved Ashley Wilkes, but the stand-out performance, in every way, is that of the mighty-bosomed Natasha Yvette Williams as the black maid Mammy, surely a shoe-in for best supported actress of the year.

-Michael Coveney