Julius Caesar, Donmar Warehouse

There’s no ignoring gender in Julius Caesar. Whether it’s Portia’s “I grant I am a woman” speech, an enfeebled Caesar likened to a “sick girl”, or Cassius raging against oppression – “our yoke and sufferance make us womanish” – the issue is written into the language and ideological fabric of the play.

Wherever there is political tyranny there are inevitably the silenced, the disenfranchised, so it seems only natural that a play like Julius Caesar should attract not one but two viable readings from the margin this year. Back in the summer the RSC gave us an all-black production set in Africa, and now Lloyd relocates the work to a female prison. Even English National Opera’s recent Giulio Cesare featured some unexpected gender-bending with the vengeful young Sesto transformed inexplicably from boy to girl.

Walter achieves a strikingly masculine presence

The coincidence has caused some discussion, with the Donmar’s Artistic Director Josie Rourke quoted as saying: “If you are a white male, you stand the least possible chance of being cast as Julius Caesar this year.” And we laugh, but not without remembering that Tim Carroll’s two all-male Shakespeares (not to mention the regular work of all-male company Propeller) have gone by this year largely unremarked in gender debates.

A veteran of turning the tables, Lloyd has already explored the disjunctive cross-casting phenomenon in her all-female The Taming of the Shrew at the Globe in 2003. Her public rationale is primarily a practical one – redressing the balance that gives women (and particularly those over 40) far fewer character roles than men in classical theatre. Pragmatic in philosophy, in practice it’s an approach that yields some exhilarating results.

Bunny Christie’s set rips open the womb-like Donmar space, returning it almost to the warehouse that gives the theatre its name. Paint peels, institutional clutter lines the corrugated walls, metal walkways circle upwards, and always the CCTV cameras and searchlights observe. In this environment, unsoftened by so much as a cushion or a curtain, Gary Yershon’s amplified rock soundtrack echoes and re-echoes, assaulting us as we share this dismal space with the grey-tracksuited ranks of prisoners.

Lloyd’s cast certainly give the lie to any weakly girlish image of the female. Strong and vigorous to a (wo)man the large cast riot over the set, wielding words and guns with equally persuasive conviction. Jenny Jules’s Cassius is all tightly-strung passion rather than a calculated schemer, and Clare Dunne’s Octavius Caesar is a disturbingly dominant force in the latter scenes. Only Cush Jumbo’s Mark Antony disappoints, turning the volume down too far on this master manipulator in the context of so loudly demonstrative a production.

The tone is set by Frances Barber’s Caesar. Sporting a black beret and trench-coat that could place her in any 20^th century conflict from the Balkans to Burkina Faso, her general is a genial psychopath, whose smiles pierce more deeply than her razor blade, who can transform a doughnut into an object of torture, a contested territory of power. Lingering on after death to direct the unfolding tragedy, Barber’s presence is pervasive even in silence, and her sprung physicality a foil to Harriet Walter’s rangy Brutus.

Walter is where Lloyd’s vision, her promise of the “heightening” effect of gender, comes into its own. Too often in conventional productions Brutus can become the limper shadow of Caesar, Antony’s too-soft rival. Here, Walter achieves such masculine presence, her troubled sincerity playing quite differently as a woman than it would coming from a man, throwing up some interesting questions about how far we’ve come from Shakespeare’s warriors and their denigrated female values. In Walter’s reading Brutus really is an “honourable man”, but still struggling to realise the violent irony of his vow to “carve” Caesar “as a dish fit for the Gods”.

Yet when you lean back from the close-up intensity of Walter (pictured right with Clare Dune as Portia), Barber and the cast, what Lloyd’s production offers is some astonishing performances framed in an over-elaborate concept, whose metatheatrical frills and furbelows are the very definition of girly. The prison play-within-a-play (already seen on London’s opera stage this month) has some practical limitations that the staging never acknowledges, and with the narrative frame only truly revealed halfway (rendering the Cinna the Poet murder decidedly bathetic) we are shaken cruelly out of the immersion built up over the previous hour and a half.

In trying to peg too many layers of political, social and ideological allusion to Shakespeare’s canvas Lloyd has muddled them, relying on the energy and physical force of her cast and the design to carry the inconsistencies. Whatever point was being made with the naked, infantilised Soothsayer (Carrie Rock) or the final too-strategic reveal for Barber’s Caesar was unclear – to Lloyd herself, it seemed, as much as to us.

Performances of emotional specificity and power carry a conceptually unfocused reading at a thrilling pace. Best to surrender to their impetus, because if you stop and think then Lloyd's feminist yarn begins to unravel.

• Julius Caesar at the Donmar Warehouse until 9 February