King Lear / The Seagull, New London Theatre, London

The sold-out production of Trevor Nunn's King Lear is not so much a fiesta of enjoyment as a test of endurance. Choppy and stodgy, it is full of mediocre, mechanical performances, not excluding that of Ian McKellen in the title role. Harsh and bellowing, he conveys no real understanding, tenderness, or remorse until the final scene, with those five famous "Never"s. There is not even the pain and mystery of madness, only more or less rage.

Christopher Oram's setting, an increasingly dilapidated theatre in pre-revolutionary Russia, is pointless and distracting. Shouting is the keynote here, whether by Frances Barber's strident Goneril, gabbling her lines like a patter song, or Romola Garai's Cordelia, thrusting her upper body forward and squawking. Ben Meyjes's Edgar makes an absurd transition from bookworm to beggar, emoting in strenuous schoolboy-grotesque. Philip Winchester's Edmund, though soft-spoken, is no more effective: lightweight and smug, he is unconvincing both as poisonous schemer and as love object for Goneril and for Monica Dolan's silly, common Regan.

The Seagull has a greater claim to being set in Russia, but only a few of the performers convince us we are there. Chief among them is William Gaunt (on press night playing the role he shares with McKellen), whimsical but heartbreaking as the aged Sorin, who is taken aback at realising that his life is over and he has never lived it. Another is Dolan, whose Masha, melting with love for Konstantin but brutal to her own devoted follower, underscores the bitter comedy of the chain of unrequited love.

Otherwise, however, both delicacy and authenticity are thin on the ground. Barber's Arkadina is less Chekhov than Coward, a shrieking prima donna without womanliness or vulnerability. Gerald Kyd's Trigorin, who looks barely old enough to grow his woolly beard, is a bizarre choice for a famous man who regrets his lost youth. And, as Nina, Garai plays all but the last scene in an unbroken fit of squeaks and gasps. Is she perpetually approaching orgasm? Is she imitating Lisa Dillon or a young Imogen Stubbs? Or is her corset just too tight?

Both productions run in rep to 12 January (0870 890 0141)