Berenice, Donmar, London; Private Lives, Festival Theatre, Chichester; Our Boys, Duchess Theatre, London

Racine's Neoclassical love triangle is rarely staged, and, on this showing, that's no surprise

It seems as if they live in an egg timer. So said the woman next to me as we took our seats for Berenice, Racine's rarely seen neo-classical tragedy, directed by the Donmar's artistic director Josie Rourke, in a new translation by Alan Hollinghurst.

And it is a beautiful egg timer in its way. A stream of golden sand is falling, from high above, in a beam of light. The stage is a dune with what looks like a handful of sea-worn chairs, half-buried.

Yet this set design (by Lucy Osborne) inevitably makes the opening lines sound slightly silly as King Antiochus (Dominic Rowan), who hails from Turkish/Syrian realms, gazes around and declares that he has never seen such splendid palace apartments. We glean that he is in Rome, in the residence of Emperor Titus (Stephen Campbell Moore) and his betrothed, Queen Berenice of Palestine (Anne-Marie Duff) – whom Antiochus obsessively adores.

Though I'll happily let the absence of opulent architecture pass, it's harder to shrug off Rourke's failure to bring into focus any issues of Western-Middle Eastern tensions or assumed cultural hierarchy. And the cast, it must be said, wear their togas and vaguely ethnic tunics and vambraces with little conviction.

The real problem with this production is the poor handling of the verse. Rowan's long speeches are peculiarly stilted; the rhythm is similar to an old-fashioned typewriter, with its jolting carriage returns. Meanwhile, Campbell Moore delivers Hollinghurst's iambics with such pat regularity that – in Act V, when the Emperor is compelled to relinquish his bride – I caught myself internally accompanying his outpouring of grief with "de-DUM de-DUM de-DUM".

One's hopes are briefly raised at Duff's first entrance. Sheathed in a gilded scarlet dress, her wide eyes spark as she romanticises Titus and his glorious lifestyle. Nonetheless, this love triangle never blazes with either passion, rage or despair. They talk of burning emotions but it's as if someone has tipped a fire bucket and quite smothered them in sand. What a bore! Berenizzzzzz.

Private Lives ought to seem slight by comparison, for while Emperor Titus's marriage vows are broken due to big political pressures, in Noël Coward's intimate comedy, Elyot and Amanda are just two old flames who can't resist each other, ditching their new spouses to hole up together in a Paris penthouse.

Jonathan's Kent Chichester Festival production is, in fact, thrilling and unusually touching. What's brilliant is the closely detailed naturalism, and the depth of the love you can feel pulling Toby Stephens' Elyot back to Anna Chancellor's Amanda in Act I – when they wander out, discontentedly, on to the adjacent balconies of their honeymoon hotel suites. This is, in too many productions, played as a shallow farce.

Chancellor's Amanda, while posing swankily with a cigarette, seems spontaneously witty. Her repartee is, palpably, driven by simmering frustration and a wild streak as she lobs jibes at her stuffy but genuinely devoted husband, Anthony Calf's Victor. Stephens's Elyot adopts a more suave manner with his clingy bride, Anna-Louise Plowman's Sibyl, but there's a gnawing, melancholic cynicism as well as irritability underneath. When he sees Amanda, it is as if an emotionally tender underbelly is exposed, in a single, silent look.

This is, quite possibly, the performance of a lifetime for Stephens. Once they're in the penthouse, he and Chancellor are both extraordinarily real and relaxed, lolling around on chaises longues with limbs intertwined, kissing and joking, having a ball as well as blazing rows. Coward's narrative twists, at the start and end, are too neat and symmetrical, but the heart of this play is wonderfully rumpled and funny and sexy. Let's hope it transfers for a London run.

Right now, theatreland is offering above par fare at the Duchess, with David Grindley's production of Our Boys, a serio-comedy set in a late 20th-century military hospital where a bunch of low-ranking soldiers wind up the newly arrived invalid on the ward, Jolyon Coy's Menzies, because he is mild-mannered, sounds posh and is gallingly on the promotional fast track. Meanwhile, the lads are surprisingly gentle with a badly injured trooper, Lewis Reeves' Ian, who is wheelchair-bound and initially barely able to speak.

Written in the early 1990s by Jonathan Lewis, this is not a great play. It's schematic and predictable. Nonetheless, based on personal experience, this is a group portrait that rings true and offers both hilarious and harrowing moments – as well as a close examination of the various levels of unjustified ill-treatment within the British Army.

Grindley unobtrusively nurtures some excellent performances. Only Matthew Lewis (Neville Longbottom in the Harry Potter films) isn't absolutely convincing, playing the ultra-dim Mick. Arthur Darvill has a sneaky, mean streak as Parry, but it is Coy and Reeves who are outstanding, along with Cian Barry as the surly Keith and Laurence Fox as the chirpy, clever but mentally scarred Joe. All in all, a strong team.

'Berenice' (0844 871 7624) to 24 Nov; 'Private Lives' (01243-781312) to 27 Oct; 'Our Boys' (0844 482 9672) booking to 15 Dec

Critic's choice

Beautiful Burnout, Frantic Assembly's high-energy depiction of boxing – part drama, part dance – tours to Warwick Arts Centre in Coventry (9 to 13 Oct). Caryl Churchill's Love and Information asks if we really know each other, or indeed know anything for sure. It's radically fragmentary but fascinating as staged by James Macdonald at the Royal Court, London (to 13 Oct).