The making of a modern Timon

Actor Simon Russell Beale and director Nicholas Hytner bring one of the Bard's most difficult characters to life

Simon Russell Beale is sitting squatly in a spillage of rank refuse – discarded take-away cartons, crushed cans, exhausted pill-packets et al – on the revolve in the National Theatre's huge Rehearsal Room One. He is wearing a dosser-style mac over his rehearsal uniform of black T-shirt and jeans; there's a supermarket trolley stuffed with flattened cardboard boxes at his side; and, in the role of Timon, he has just been performing a run-through of a sequence that ends with him hurling violent abuse and a rock at the cynic Apemantus, played by Hilton McRae.

A brief discussion about that rock then ensues with Nicholas Hytner, the NT's artistic director who is mounting this modern-dress and freshly adapted revival of Timon of Athens, the tricky Shakespeare/Middleton collaboration now in preview in the Olivier as part of the Travelex £12 season. Russell Beale's face lights up with scandalised glee at the thought that he may be required to score a direct hit with this missile. McRae contributes the view that he dislikes the feeble sound that a papery fake rock makes when it hits the stage. Hytner says he's more concerned about the damage that a concrete version might do to the Olivier stage and to McRae. Russell Beale temporarily resolves the issue by announcing, with twinkling modesty, that, "I'm not such a good shot".

It's a typical piece of camp self-deprecation. But while he may not be the go-to man where prowess at a coconut-shy is concerned, audiences have come to expect nothing less than constant bull's-eyes of character interpretation from this most acutely intelligent of actors – renowned for striking the target from unexpected and deeply individual angles. He once famously described the art of acting as "three-dimensional literary criticism" and he has said that he begins by trying to rid his mind of all the received wisdom and preconceptions about a role. He then sees it as his job to guide the audience through a carefully constructed argument that is supple enough to embrace contradictions and to leave him open, as an actor, to the inspiration of the moment.

It has been fascinating for me, in the past few weeks, to watch Russell Beale put those principles into practice. I was allowed to sit in on a couple of lengthy rehearsals for this production. The actor is on our screens at the moment as Falstaff in the BBC's Hollow Crown season. From playing one of the Bard's most popular creations, he has now switched his attention to one of the least-loved protagonists in the canon, as rigid as the fat knight is promiscuously flexible. Timon starts off as a compulsive philanthropist but, when he over-extends himself to the point of ruin and the spongers and sycophants who were his fair-weather friends refuse to bail him out, he simply switches from one extreme to another, turning into an even more fanatical misanthrope who rages at mankind.

The atmosphere in the rehearsal room was notably good-humoured and this clearly stems from the rapport between Russell Beale and Hytner, who have often worked together and are very much on the same wavelength: quick-witted, ironic, Cambridge educated and preternaturally alert to verbal nuance.

"I'm just going to worry away at this and drive us all mad," Hytner declared at one point as he pushed his more-than-willing cast into probing ever more deeply for the precise and propelling emotional logic of the scenes in this difficult text. But the focus is not so intense that there aren't some amusing tangential flights as when director and star suddenly start swapping impressions of The Song of Achilles, the Costa Prize-winning romance about same-sex love in the ancient world which they decide is "chick-lit for gay men written by a chick".

Academic criticism of Timon tends to give salience to the theme of ingratitude. But Russell Beale tells me that they have found that the play is more fundamentally preoccupied with the nature of friendship and the hero's fatal misconceptions about it: "Timon completely misunderstands what true friendship involves. He absolutely equates it with profligate gift-giving". He reveals this while showing me sketches of Tim Hatley's designs.

Each successive run-through of the banquet scene sharpens the impression that Russell Beale's Timon dispenses his ludicrous largesse as a way of fending off, rather than promoting, intimacy. He may work the dining table wreathed in bonhomous smiles but you notice how he freezes awkwardly in the embrace of young Ventidius whose cheque, in repayment of a loan, he rips up ostentatiously with the unctuous declaration that "there's none/ Can truly say he gives if he receives". Further details are added that embellish this sense of emotional repression in a hero whose glazed displays of extravagant philanthropy increasingly look as though they may be the reflex of a deep and unacknowledged sense of inferiority.

The public persona as the private self turned painfully inside-out: Simon Russell Beale has always had a genius for hinting at this.

One remembers the fat Restoration fops he played in his early days at the RSC, where their screaming exhibitionism and social competitiveness gave off more than a whiff of putative wastes of onanistic loneliness and fear behind the scene.

So, in the other rehearsal I witness, the down-and-out, raging misanthrope who eats with his fingers from refuse bags, who finds a hoard of gold ("a cosmic joke," declares Russell Beale, "like an alcoholic being offered a drink") and who drives away his visitors – this figure feels like the accident that was always waiting to happen because of something in the hero's nature. I watch the detailed fine-tuning, over several re-runs of the Beckettian double-act of Timon and Apemantus, the party-pooping cynic who, to everyone's discomfort, cuts straight through the falsities in the banquet scene.

Timon of Athens is not a play renowned for filling theatres and this production will enjoy a long run in the Olivier repertory, before transmitted live to cinemas round the world on November 1. But if anyone can put bums on seats in the title role it is Russell Beale. For there is no actor on the planet who can make you empathise more keenly (and, indeed, identify) with characters who cannot love themselves and have to live – and die – with the consequences of that failure.

'Timon of Athens', National Theatre, London SE1 (020-7452 3000) to 1 November; 'Henry IV – Part 2' is on BBC2 today at 8pm