I go to Denver for the third month of rehearsal of Tantalus.

It's been a bumpy ride. Weeks before rehearsals, Jane Lapotaire, one of four English principal actors in the Anglo-American Cast - a leading classical actress in England, and a star on Broadway as Edith Piaf - pulled out because of illness. Ann Mitchell has taken over as Hecuba and the Nurse. Then David Fox, a wry old fox, pulled an Achilles tendon - he had to choose a body-part with a classical name, of course - and has been rehearsing in a wheelchair. Mick Gordon, Edward Hall (Peter Hall's son) and Mick Sands - the two co-directors and the composer - had no sooner arrived than they had to be flown back to Britain because their US visa applications had been screwed up. Peter, already anxious about the great mountain they have the climb - the 15 hours of drama in six months' rehearsal - laments over the phone that three weeks have been lost.

Its gets worse. John Barton, who has been equipped with a visa, offers to help Peter out in his crisis, and settles into the neighbouring rehearsal room, "just working on text with some of the principals". The trouble is that meanwhile, next door, Peter is cutting and changing the first half of John's first play, which Peter is convinced is too leisurely.

It gets even worse. Larry Lamb, one of the four English actors, who seemed good in audition, has been working hard, but isn't working out. In a painful scene, which traumatises the younger actors, he's fired, or in that mealy-mouthed American euphemism, "let go". A scramble around New York brings Greg Hicks, who played Orestes in Peter's Oresteia at the National Theatre - and is now played the Orestes-based character in TS Eliot's The Family Reunion - to play Agamemnon and Menelaus. Then John Carlisle, another senior English actor, resigns in the eighth week, saying he will not play in masks, he doesn't think masks are right for John's play. A further desperate hunt via cellphones tracks down Alan Dobie in the Old Kent Road. Without having read the script, and out of loyalty to Peter, he flies in to play Odysseus and Calchas, Apollo's priest.

These crises have accumulated like some curse from Zeus before I arrive in Denver....Firestorms are raging in the Rockies, the sky is overcast with grey. A comparable cloud of conflict hangs, like the rock threatening Tantalus, over the long days of rehearsal. A Chorus of nine young women thread through all the plays, American women of every aspect - black, Asian, white. I watch them warming up, loosening joints, shaking out limbs, tuning up voices. They have an ungrateful acting task, like every chorus; they have to act as a flock of people, reacting to events, rarely becoming individual characters.

After rehearsal, I go to see Dionysis Fotopoulos, the designer of Tantalus, in his office, a dim-lit cavern lined with oriental rugs and gods, flaking Mediterranean pillars. Dionysis has worked with Peter Hall over the past decade, designing among others a lurid Lysistrata and a stark King Oedipus. His inventiveness inspires Peter. In his workshop, flanked by two attentive American assistants, he draws character distinctions on photocopied blank masks. Long hair for Achilles, dropped eyelids for Agamemnon. An occasional mutter to the assistants: "Raised shoes for Neoptolemus". It's quiet in the workshop. A crowd of plaster face-casts of the principal actors stares stonily into the work-clutter. Each actor has to submit to a blue plaster face-bath, from which their features have been frozen. Another long pause from Dionysis, chalk poised over the paper. "Now how do we do Odysseus?" he murmurs. "His snakiness. The man who takes a straight path."

The day before I leave, I catch Peter in his lunch break, slumped at a table in his office, reading a magazine. His eyes look bloodshot. We talk in a desultory way. Next day, he's in hospital with an eye infection, a condition he's had for years, he says, and which always flares up under stress. Before examining him, the eye doctor at the hospital asks him what religion he is, a routine enquiry to make sure he would wind up in the correct cemetery in the event of fatality. "I said I was a militant atheist," says Peter. "He didn't find that funny." What would John Barton say if he were asked the same question? He shares with Peter a love of dialectic and argument, but there's something more: not mysticism, which he abhors, but certainly relish in mysteries, a philosophic curiosity about the mystery of things.

I fly back to London, on the same flight as Don Seawell and his producer, who are coming over for a summit meeting about the English tour of Tantalus with all the theatres that are ready to present Tantalus if the deal is right. There's still a shortfall of £232,000 which, if not met, will put the entire tour in jeopardy. I have detected a coolness from Don Seawell towards me. He must have expected me to raise more funds for the production than I have succeeded in doing. So as we're both waiting at Heathrow baggage reclaim, at six in the morning, I try to make amends to our dapper, octogenarian backer. I shouldn't have tried, I'm tired and clumsy and it all comes out wrong, as I say that fund-raising may not be what I do best, that perhaps I'm not really that sort of producer, that I have brought a good deal to the production, and that I am still trying to raise the tour's fund shortfall. I am never to hear the end of one phrase, "I'm not the sort of producer who raises money". For him, it becomes: "You are not a producer, as I understand the word."

- Excerpted from theatre@risk by Michael Kustow, published by Methuen, 10 May 2001, priced £12.99.

On Wednesday, 9 May, Kustow will be talking about theatre@risk at Samuel French's Theatre Bookshop, 52 Fitzroy Street, London W1. Tantalus is playing at the Barbican Centre from 2 to 19 May 2001.