Timon of Athens, Olivier, NT, London / The Complete World of Sports, Arts Theatre, London

The super-rich are always with us, a few so generous they are immortalised in stone: the Sackler Galleries, the Sainsbury Wing, the Duffield Studio. And here is another, his gift to the National Gallery so great that, at the National Theatre, we are at a present-day party to unveil the Timon Room – sipping champagne before El Greco's swirling picture of Christ overturning the tables of the money-changers.

The capital's A-list is in attendance – the dress-down poet, the chippy artist, the sulky philosopher who never takes his coat off, as though he is not really in the room, the sycophantic, the greedy, the vain. And what ensues is a tale of trust betrayed that's so vivid we could blush. For Nicholas Hytner has raised Shakespeare's sketchy and tarnished Timon of Athens, chipped off the barnacles, encrusted it with jewels in the shape of lines from other works, and revealed a miraculous, unexpected treasure.

Simon Russell Beale strides from open hand to open hand in a fine suit and a good mood as wealthy Timon, transplanted by Hytner to modern-day London, giddy with giving, ever in demand. The privileged who dine with him know they are in for a treat in his Belgravia residence. The Royal Ballet dances between courses. He bails out a friend, gives an impecunious suitor a dowry, entertains the chirruping flock from Fashion Week. And then, in this topical fable, as his fortunes turn, so do the backs of his friends. Three times he is refused help, each excuse more inventive than the last, an especially comical performance here from Tom Robertson as shallow hooray Ventidius. The finance sector, the arty set and the influential shut him out. At one final dinner, Timon wreaks a terrible revenge before taking to the streets, a toxic, trundling troll.

In an abandoned building site (design by Tim Hatley), he stumbles on a means to fund the Occupy-style enemies of the status quo and so once more attracts attention, now unwanted. The vanity of riches could hardly be more topical, and this remarkable production's audience is well primed for Shakespeare's eye-popping parable. Once a muddly makeweight in the First Folio, this Timon has the heartlessness we find in Lear, the isolation of Hamlet, and a defence of institutions targeted for the wrongs of those beyond their walls.

With some male roles transferred to women, the dozens of characters not always distinct on the page gel instantly: servant Flavius becomes Timon's loyal PA Flavia (Deborah Findlay), economising at Iceland. The senator Sempronius mutates to Lynette Edwards's brittle MP Sempronia; the artist is Emin-like Penny Layden. Snarling at everyone, Hilton McRae's Apemantus is not so detached that he refuses a place at table: even philosophers have a price.

The noble values of sport would, of course, never be compromised by financial incentive, but at the Arts Theatre the Reduced Shakespeare Company finds daftness aplenty in its breakneck history of biffing, sliding, and going round in circles.

The Complete World of Sports, from cavemen to the Games, is circumnavigated with the company's much-loved madcap irrreverence, an agreeable giggle from pistol to podium. New York Yankees' Yogi Berra sums up: "Baseball is 90 per cent mental; the other half is physical." Odd that he never funded a gallery; or ran a bank.

'Timon of Athens' (020-7452 3000), in rep to 31 Oct and at cinemas nationwide 1 Nov; 'The Complete World of Sports' (020-7836 8463) to 25 Aug