The RSC concludes its Rome season with one of the less frequently performed of Shakespeare's ancient history plays, the tricky and awkward Coriolanus. Arguably highly pertinent for its study of patrician hubris in the face of popular dissent, the play was written after the great masterpieces of Hamlet and King Lear, and contains one of the Bard's most opaque titular heroes.

Much has been made of the casting of RSC debutant Sope Dirisu as the great warrior who defends Rome courageously, only to be banished for his arrogance and disdain for the mob. The young economics graduate emerged through the company's Open Stages programme five years ago and has been handed the challenge of taking on the giant role as his first job in the main space.

The decision by season director Angus Jackson places a vast weight on Dirisu's shoulders, and his demeanour and imposing presence certainly rise to it. I was less convinced by his delivery, which hovers around a high tenor for much of the performance and lacks the range and gravitas necessary for such a forceful character. In addition, there is hardly any acknowledgement of, or relish in, the poetry and splendour of Shakespeare's language.

In this, sadly, he is paralleled by much of the rest of the company, with a few notable exceptions. It's almost as if the entire play has been rewritten as naturalistic prose, with any discernible line endings and rhythmic pacing deliberately excised. The effect is to deaden and flatten the speeches, rendering them unimaginative and curiously bland.

What the production lacks in poetry it seeks to make up for in vigour and spectacle. Robert Innes Hopkins, who has designed the whole season with a continuous but varied theme, this time takes his palate firmly into sombre darkness, aided by the dim, industrial lighting of Richard Howell. The modern dress works well enough, and if the pre-show forklift truck manoeuvre (which earns a well-deserved round of applause, incidentally) feels gimmicky, at least it sets the tone for the performance to come.

And what of those notable exceptions? Interestingly, quite a number of the smaller roles among the huge throng on stage stand up well to scrutiny. Among the larger parts, the wise elder statesman Menenius is in the more than capable hands of another wise elder statesman, associate artist Paul Jesson. Whenever he's on stage, he holds the attention effortlessly, and his delivery is both impeccable and consistently intelligible. Similarly, Haydn Gwynne as Coriolanus's mother Volumnia brings a combination of aristocratic arrogance and maternal vulnerability that is particularly moving.

The production runs long, and even with plenty of well-rehearsed battle action and fast scene transitions manages to feel a little ponderous at times. But, as the culmination of an ambitious, thoughtfully realised season of some of Shakespeare's less popular works, it solidly earns its place in the RSC's Roman canon.

Coriolanus runs at the Royal Shakespeare Theatre, Stratford-upon-Avon, until 14 October.