Mid-afternoon in the suffocating heat of the Moroccan desert, and a day that began long before dawn is at last building to its climax. On a ridge, overlooking a rugged, rock-strewn valley, a swarm of make-up artists, costume-fitters and prosthetics experts are applying the finishing touches to the loincloth-clad figure of the actor Joseph Mawle. Nearby, in-between swigs from small bottles of mineral water, a quartet of red-robed Roman centurions is rehearsing hauling upright the crude, T-shaped gibbet to which the young Englishman is about to be attached.

Until now the day has been bedevilled by small technical hitches that have put back filming. Mawle, facing the biggest challenge of his young acting career, portraying Jesus’s crucifixion at Golgotha, has been up since 3am. So when, a few moments later, the last-minute adjustments are complete and the call for quiet and then action finally goes out, the sense of excitement is mixed with a palpable sense of relief. Hundreds of hours of preparation and planning, both here in Morocco and back in the UK, are about to come to fruition. Or so it seems.

Seconds after the cameras turn over for the first time, a sudden gust of desert wind throws thick, red dust up into the eyes of Mawle and the centurions. Within moments tripods, chairs and other bits of equipment are being picked up and thrown over by stinging blasts of air. As all eyes turn heavenwards, a bank of dense, livid, purple and grey clouds is settling above the scene, obscuring even the vast Atlas Mountains in the distance. Soon fat gobbets of rain are turning the dusty landscape a dark, muddy brown, sending everyone running for cover. Minutes later, with the storm growing in intensity, filming is postponed.

At least producer Nigel Stafford-Clark hasn’t lost his desert-dry sense of humour. “There are times when I wonder whether I’ve walked into the Book of Job. This definitely feels more like it belongs in the Old Testament rather than the New one,” he says, huddled under a makeshift tent, looking up at the unruly heavens with a world-weary smile. “I do feel like having a conversation with God and saying, ‘Come on, we’re trying to tell this story, give us a break.’”

Stafford-Clark and his team are here in southern Morocco, near the town of Ouarzazate, to film an ambitious new, three-hour version of the Passion, the story of Jesus’s last week on Earth. Despite the fact that it is summer, this is the second time in a week that the production has been thrown by the capricious Moroccan weather. Last week, plans to film Jesus’s arrest by the Romans in the Garden of Gethsemane were wrecked by a sudden and unexpected flash flood. “It was extraordinary. One day this place looked like it hadn’t seen rain for centuries, the next it was submerged in water that was roaring down from the mountains,” says Stafford-Clark.

Stoicism is the television producer’s stock in trade, but rarely can it have been required in such quantities. Encounters with biblical storms are far from the first tests Stafford-Clark and his production team have faced. Given the bold, brave and potentially controversial approach they are taking to retelling the story of Jesus’s final days, they are also unlikely to be the last.

The BBC conceived a new version of the Passion, to be broadcast episodically at prime time on BBC1 over four nights through Easter Week, more than a year and a half ago. The appetite for Biblical stories had been proved by the enormous box office success of Mel Gibson’s film The Passion of the Christ. Stafford-Clark, who had just brought the acclaimed Bleak House to television in a similar format, sensed an opportunity to breathe new life into the subject.

“I had just watched Pasolini’s Gospel According to St Matthew, which I’d loved when I’d seen it in the Sixties,” he says, by now safely installed in his office at the nearby Atlas film studios, which have become his base. “It is the only successful version I’ve seen of this story. The big American epics in the Fifties, and even the Zeffirelli version with Robert Powell back in the Seventies, were all very reverential. They all made you feel as if you were looking at it through a plate glass window, as if there was a distance between you and what was going on,” he says. “It always felt like King Arthur or Lord of the Rings, as if these events took place in a vacuum.”

Stafford-Clark wanted to ground the story in reality for the first time. “It’s billed as the greatest story ever told and in many ways it is. But in terms of storytelling it never seemed to make a lot of sense. Watching all these other versions, I didn’t understand what Palm Sunday was all about, for instance. He was just a humble preacher from Galilee. Why all this excitement? Why did the high priest react the way he did in condemning Jesus to death? Why did Pilate do what he did? When you are given the story normally, all these things have to be taken for granted. They are part of what you are told. I felt there was a chance to remedy that.”

The key, for him, was to create a drama that allows the audience to feel as if they were in the thick of the action 2,000 years ago. “If you had been in Jerusalem in AD32 you would have witnessed this. You would have seen the crowds, the excitement of his arrival, you’d have got wind of what was going on in the temple. And then you’d have heard rumours that he’d been arrested,” he says. “It’s something that actually happened. This is the thing we are trying to get across.”

The first challenge was to find a writer capable of evoking the turbulent, chaotic political melting pot that was first-century Judaea. He appeared in the unlikely form of the Emmy-winning, Irish-born writer Frank Deasy, best-known for hard-hitting contemporary dramas like Real Men, about child abuse, and Looking After Jo Jo, set in the world of Scottish drug gangs. Deasy’s fast-moving, episodic script shows the tumultuous events of Passover week in Jerusalem from the perspective of all those who took part in it, not just Jesus and his disciples, but Pontius Pilate, the Romans and the Jewish temple authorities too. “As a dramatist, the big challenge was to evoke a world in which this story has not taken place, a world without Jesus or any Christian churches or any of the Christian concepts that are so familiar to us,” he explains.

As well as reading the Gospels and conducting his own research, Deasy spoke to Professor Mark Goodacre, a leading New Testament scholar at Duke University in North Carolina, who was engaged as a historical consultant to the series. It allowed him to add dramatic depth – and potentially controversy – to the orthodox version of the story. Deasy was determined that every character had a story of his or her own. “By the end I hope people feel they have been on a very deep journey with these characters, that they feel they have shared the most powerful week of their life. So everyone had to have a motive that we could understand, a logical psychology to the things that they do,” he explains.