Howard is playing Oedipus (a role so long it makes Hamlet look like a bit part) and embracing anonymity for the first time in his career. As indeed are the majority of the others. Only Greg Hicks and Pip Donaghy, veterans of Hall's astonishing, bold and brilliant full-masked all-male production of The Oresteia staged 15 years ago, know what is expected of them. No doubt they mentioned that two actors withdrew with nervous breakdowns. According to Peter Hall, the problem wasn't being hidden but, paradoxically, confronting those aspects of themselves that a mask exposed.
By all accounts, acting doesn't get much tougher than this. On the first day of rehearsal the cast received a card from Judi Dench, saying she had been thinking of them all and wishing she was part of it - until she remembered the masks and felt profoundly relieved she wasn't. Anna Massey turned down the invitation to take part. "So desperately demanding - and I'm not sure I could do it," she confided. Doubtless she could have, but not without more than a little suffering, if today's workshop is anything to go by.
It's very easy to get terribly camp and holy about masks, partly because of the rigmarole involved. The initial preparation requires the actor to choose a mask that appeals instinctively, look at it, look at himself and the mask in the mirror and, if it offers anything to him, look at it again until he feels ready to become part of it. Then he puts it on, looks in the mirror and, if all the jiggery-pokery is working, he gets an extraordinary charge from the mask.
That's the theory. This is the practice. Alan Howard chooses a diaphanous red cloak and one of the more melodramatic masks from The Oresteia, which took the Aeschylean cue for Gothic horror, and nips out into the corridor, drapes them on to a post, lights up and surveys the effect, cocking his head this way and that like a bird. After a good quarter of an hour, he nods slowly and sagely, and drapes and masks himself. Suzanne Bertish winds a shawl around her face and puts the mask on top of that, then sits down cross-legged. A lanky actor piles a heavy black cloak on his head and resembles a bizarre and exotic Greek Orthodox priest. Most of the figures seem to be beseeching. Some scratch rudely. No one speaks. Alan Howard breaks the silence with a hearty "Hello there" and shakes a fellow Thespian by the hand.
That gets Pip Donaghy going. "A surge of choler and grudge sweeps over my spirit," he says, endlessly repeating this line of Electra's from Tony Harrison's Oresteia. "What do we want?" says someone rather revealingly. Silence. The knocking is Suzanne Bertish bashing her masked head against the wall. A wee drama ensues in which a convincingly old and decrepit crone squabbles over a walking staff with another frail-looking androgynous figure. In the end they make friends. The scene makes bizarrely compelling viewing.
Silence. Some choose the subterfuge of acting, Alan Howard puts out his arms and runs around like a child playing aeroplanes. Others curse. "Fock you, fock you," spits someone at no one in particular. Some feel nothing at all. By now several more crouch despairing in the corner, spectators rather than participants. Greg Hicks casts aside his third mask, disrobes and curls up in a foetal position on the floor, his back to the action. The silence is cut by Alan Howard bursting into an aria of the first 20 lines from Christopher Logue's Iliad.
Hall peers at them all over his half-glasses with an expression of amused benevolence. "This always happens," he chuckles. "I've never known it not happen. Put a mask on a group of actors and, if they do anything at all, they become very primitive. Most can't talk - the words won't come out - or don't want to talk. Others get very aggressive and cry and shout and hit out like small children. The mask does that. We contain in ourselves all that we have been and might be and the mask can take you anywhere - to the feminine side of yourself, the brutal side of yourself, the old side. It's a completely liberating device. That sounds terribly Pseuds' Corner but it's true, don't ask me why, it's one of those mysteries. If it's not working, you can see the actor underneath and that's horrible, that's false."
Greg Hicks had felt precisely that. "I felt fake, phoney, shallow. For me, the mask is a barometer which always exposes if I'm going for an effect instead of for real depth. It's an extraordinary process. The thing I find about wearing a mask is that your acting ego is severely reduced because you are invisible. You have to surrender your ego to the mask. When it goes well, it's like having an encounter with something other than yourself, something other-worldly and not necessarily kindly - it depends what the mask is like. You can be transported and feel immense power. The thing I love about masks is that the moment you take it off you get rid of your performance, you don't carry the character home and agonise about it."
Hall's passion for masked theatre stems from a belief in the potency of the mask which allows the actor to experience emotions "much more animalic and enormous than you can easily express with a naked face. If you scream with a naked face, the response of an audience is to recoil, but if you tell them about a scream through a mask, it's the Munch painting, isn't it? Silent and frozen and absolutely horrifying. It has a form like a mask." The process of "getting a mask to speak and cry", however, is complex and long. "You can see when the mask ceases to be a barrier and actually expresses the body," explains Hall. You can't, however, short-circuit the time needed for the mask to grow up, he explains, therefore mask work and text work have to be done independently until a point is reached when the actors know the form and the rhythm of Ranjit Bolt's version of Oedipus as well as the steps of a dance. "Then they can make it their own and act it."
One month on and much has changed. Spring has become summer. Today is devoted to text and, at the back of the room, lifeless rehearsal masks lie in coffin-like boxes. In place of the severe man-in-black, Hall appears laid-back in crumpled washed-out linen. His own mask, one assumes. His text rests on a music stand. He holds his pencil like a baton and scans five beats to each line with a pedantry verging on the fanatical. Ranjit Bolt may not be Shakespeare, but Hall is treating his text with similar scrutiny. The thrillingly rich range of tones and timbres that make up the Chorus ripples through the speeches. A drum beat marks the emotional pulse. Having thrashed out where they are going and how they are feeling through every line, the cast respond emotionally as one, moving across the stage like a shoal of fish. Once masked, the sound will emerge as if from one body, only the voice will reveal who is talking. "Lean on those sibilants," says Hall. "Control the emotion with the Ds." Hall is a subtle director. He wins actors' trust readily, encouraging input but always getting the final edit. Only where verse-speaking is concerned is the policy non-negotiable from the start. Actors must mark the beginning of the line, obey the caesura and half-lines. The effect is revelatory, electrifying, even without the masks. "Keep the active statements up. Don't break the line structure. Be aware of the irony. Sophocles is deeply ironic," insists Hall. Cues are missed, unimportant words stressed, confidence quickly lost when Hall frowns and easily won when he smiles. "This is getting good. This is nice, very nice." You realise how much of acting is physically exhausting and repetitive and very boring and yet, through all the fits and starts, tragedy emerges with appalling clarity.
"I always loved these two plays," says Hall. "But I've been surprised to find how rich and compulsive they are, specially Oedipus in Colonus, which tends to get written off as an old man's play, elegiac, resolved as Oedipus goes gently towards death and a silvan grove. It's not that at all - it's a very turbulent play about settling scores, much like King Lear. The other thing I've discovered is that the essence of Greek drama is the mask, not just the mask the actor wears, but the mask the stage wears because horrible things always happen off stage. The stage is a mask, a form to allow you to deal with primal feelings and primal passion. And the key is the Chorus. The play isn't about Oedipus, who is on the stage for us as the suffering leader, but about Oedipus's effect on the Chorus. Yet the very words 'Greek Chorus' fill one's heart with dismay, don't they? I've read all my life about how wonderful the Greek Chorus is, how they danced and sang, and have the best speeches - and from what I've seen, I find it very hard to believe. They just stand around like lemons saying 'Oh, Thebes'. It's time we changed that." If he pulls it off, it will be well worth the 2,500-year wait.
n 'The Oedipus Plays' opens in Epidaurus, Greece, on 30 August and previews at the Olivier, National Theatre, from 7 September (0171-928 2252)