Julius Caesar, Roundhouse, London<br/>The Potting Shed, Finborough, London<br/>The Painter, Arcola, London

A smooth, politically savvy Brutus falls in with a bloody assassination plot in a triumphant RSC production

Greg Hicks enters punching the air, striding so fast it's as if the cheering plebs have catapulted him on-stage.

Parading at the festival of Lupercal, Hicks's Julius Caesar is more exultant warlord than ceremonious emperor. You can almost see the charisma spraying off him as he wheels around, a fur cloak slung across his sinewy, bare torso. Having crushed Pompey, he now senses that the crowning glory – kingship – is within his grasp.

A month is a long time in politics. In the theatre, too, it's seen a remarkable turnaround for the RSC's London season. By comparison with December's dire Antony and Cleopatra, Lucy Bailey's production of Julius Caesar is a triumph. She renders Shakespeare's drama grippingly tense, highlighting how its politicians – while paying lip service to comradely ideals – are driven by feral one-upmanship. Though a superpower, Ancient Rome is still brutish.

In terms of violence, Bailey takes the bull by the horns. Two snarling, mud-caked slaves re-enact the lethal fight between Romulus and Remus, the city's founding wolf-boys. In contrast, Sam Troughton's Brutus looks a pristine young politician – puritanical in his long grey tunic. Yet as John Mackay's Cassius presses him to join a nominally noble alliance of assassins, Brutus's eyes goggle with terror and ambition. Troughton hits his stride enthrallingly in this role.

With wives cast aside in the pursuit of prowess, Brutus and his co-conspirators are soon butchering Caesar. Encircling Hicks on his marble dais, they take turns to leap up, stabbing him until he sloughs down the steps, showering blood. Then Brutus suddenly takes command, virtually barging Cassius off the plinth – no democratic team-player, but the next potential megalomaniac.

Darrell D'Silva's Mark Antony proves storming, too – an uncouth, boozing bear of a man, who delivers his great funeral oration ("Friends, Romans, countrymen") not as silver-tongued rhetoric, but impassioned rabble-rousing. His voice cracks with indignation at the "honourable" murder.

The production could still improve. The crowd choreography and video projections, by William Dudley, need fine-tuning, though the idea of showing milling throngs of Romans on layered screens is potent.

In Graham Greene's creepy drama The Potting Shed, James Callifer (Malcolm James) is a mentally unstable divorcee – perhaps bipolar, as Greene was – haunted by a repressed memory. The big mystery is what happened to Callifer as a boy, in the garden shed, after which he was cold-shouldered by his tight-lipped, scientific family. His desire to learn the truth drives him to track down the family renegade, the ostracised uncle William (Martin Wimbush), now a raddled, alcoholic priest.

The Finborough's intriguing revival looks as if it's about to expose a paedophile Catholic cleric, which would have been stupendously radical in 1958. Instead, Greene's plot turns religiose with an alternative revelation that's extremely hard to believe – unless you're a born-again, perhaps.

East London's wonderful Arcola Theatre gains a second lease of life, moving to Ashwin Street's Colourworks factory, once home to Reeves whose watercolours J M W Turner used. The conversion is work-in-progress, but the main auditorium delights: rough-and-ready yet snug, a sunken chamber of old brick with a thrust stage of raw planks.

Mehmet Ergen's opening premiere, The Painter, is an intimate portrait of Turner, played by Toby Jones as a shy, absorbed eccentric. Writer Rebecca Lenkiewicz interleaves his establishment-challenging ideas on landscape painting with his troubled relationships with women – deranged mother (Amanda Boxer); prostitute (Denise Gough); and mistress (Niamh Cusack). Understated and quietly superb.

'Julius Caesar' (0844 482 8008) to 5 Feb; 'The Potting Shed' (0844 847 1652) to 29 Jan; 'The Painter' (020-7503 1646) to 12 Feb

Next Week:

Kate Bassett catches Rebecca Hall in Twelfth Night, directed by her father

Theatre Choice

Rory Kinnear excels in Nick Hytner's often startling production of Hamlet, back for a further run of performances at the NT Olivier, London, to 26 Jan. Katie Mitchell directs an insomniac Sandy McDade in a low-profile studio premiere of Small Hours at London's Hampstead Theatre, to 5 Feb.