Twelfth Night, Donmar Warehouse, London

He looks as though his copious blubber has been constrained from birth in a buttoned-up pinstripe suit and that he probably emerged from the womb with that self-important beard and moustache.

His gait is an officious cross between a march and a scamper; his tone is a fruitily sibilant sneer; and he is forever consulting his watch with righteous impatience. At night, his locks are wedged in a hairnet.

And yet Simon Russell Beale's magnificent Malvolio is by no means a figure of fun in this diverting version of Twelfth Night, directed by Sam Mendes in a spare, warmly candle-lit staging, with costumes that range from the Edwardian era to the Thirties. No one is better than Russell Beale at showing you the tragic intensity of non-tragic people in ridiculous predicaments.

Twelfth Night now joins in rep, with the same crack ensemble, Mendes' production of Uncle Vanya. Both are plays about bruised illusions, unrequited love and misplaced sexual desire. They have shifting, precarious moods, the comedy shot through with melancholy.

And Malvolio accrues an abused humanity that bears comparison with that of Vanya, the steward in Chekhov's play – thanks to Russell Beale, who performs both roles, and to Mendes' acute direction.

It's a brilliant touch that the scene where Malvolio is gulled with the letter takes place not in the garden but in his bedroom, with the tricksters behind a screen. It's painful to watch the sincerity with which Malvolio slumps to his knees and addresses the apparition of Olivia (an amusingly sexy Helen McCrory) in the silver picture frame at the back.

This frame acts as a threshold where characters who are in the thoughts of others appear. Emily Watson's attractively understated Viola enters through it when she arrives in Illyria. Her brother stands within it, when Antonio's confusion gives her hope that her sibling has survived. And at the end, the frame keeps within our view the blindfolded Malvolio, whose vow of revenge has ominously quiet sanity.

The production perhaps feels a little land-locked for a play where "tempests are kind, and salt waves fresh in love!" but it is full of imaginative touches. Like Vanya, it is booked solid, apart from a few tickets that can be queued for each day. If that fails, it would be well worth trying to tunnel your way in.