Danny Boyle: 'Yes, we did betray Ewan'

What a wicked ruse it would be to sell 28 Days Later as the new film from the director of The Beach. On the one hand, that's precisely what it is. But it's also the picture that marks a return to the grubby, lo-fi vitality that had all but vanished from Danny Boyle's work in the seven years since Trainspotting. Anyone turning up in anticipation of Leonardo DiCaprio-calibre eye-candy is likely to need carting out of the auditorium on a stretcher. "It's not a normal film," Boyle says. "It's not a romantic comedy." That's called stating the bleeding obvious. That's stating the bleeding obvious elevated to an art form.

28 Days Later is a zombie movie, but not your common-or-garden kind. It's a zombie movie with a head and a heart – as well as the obligatory severed limbs, gouged eyes, punctured organs, and so forth. It nods in the direction of George A Romero – one sequence in a supermarket inevitably calls to mind Romero's 1978 Dawn of the Dead, except that Boyle's version takes place in a branch of Budgens. But amid all the nasty frights and general beastliness, Boyle has crafted a disquieting portrait of Britain that owes more to this country's tradition of desolate, appalled surrealism – Lindsay Anderson's O Lucky Man!, Patrick Keiller's London, Tony Harrison's Prometheus – than to any straightforward genre shocker.

The tone is established by the nature of the virus that reduces most of the British population to walking corpses: not, as you might expect, an overexposure to TV shows like Fame Academy and Model Behaviour, but contact with a lethal strain of distilled rage. This Cronenbergian concept launches one of the most dynamic opening reels that you're likely to see this year, as a motorcycle courier named Jim (Cillian Murphy) rises from a 28-day coma to find Britain drained of its vital signs. When Charlton Heston discovered that he was the last soul on earth in The Omega Man, you felt he had been long equipped to deal with that likelihood: you never caught a whiff of dread. But the sight of the perpetually haunted Murphy drifting up the silent Mall, or wandering in the sightless gaze of the London Eye, is fiercely disturbing.

Partly, it's that the images capture the serenity of the aftermath of inconceivable tragedy. But there's also the kick of uncomplicated spectacle that connects us to those audiences at the first Lumière Brothers films: we are too sophisticated to faint or flee as they did, but like them we may have cause to doubt what we are seeing.

"Everyone loves those London shots," beams Boyle, and indeed, it's a minor problem that nothing else in the picture quite equals their primitive power – not even the sight of the M1 without traffic. "We originally had those 28 days written in the script, and we were always terrified of shooting them – either that we wouldn't be able to afford it, or we'd cock it up. That sort of thing is never done very well at our level." So they just dropped the scenes. "Atmospherically, it was a great idea to plunge the audience into the action with Jim, knowing only as much as he does. And it was also a good way of saving $2m."

Money seems much on Boyle's mind, as it must be to any director who has made a film as colossal and uncontrollable as The Beach and lived to tell the tale. He still speaks highly of Leonardo DiCaprio, but ambivalence drips from his reminiscences about that picture. "Nothing is accidental on a movie that size, and that doesn't suit me. I treasure spontaneity. This was like an oil tanker. It's weighed down with riches, but it drifts round very, very slowly."

Then there was his intention to "give something back to Thailand" by hiring a Thai apprentice to shadow every British crew member. "We were hauling 300 fucking people around wherever we went. And you know how hard it is to learn Thai names. Every lunchtime was like a prime minister's reception." The film still gives him cause to grumble. "I cut it to shreds. I look back and think: Why did I cut that? But you make mistakes."

Straight after finishing The Beach, Boyle pitched up in his native Manchester with the cinematographer Anthony Dod Mantle (whose credits include Festen and Lars von Trier's forthcoming Dogville) to make two BBC films on digital video – Strumpet, with Christopher Eccleston, and Vacuuming Completely Nude in Paradise, starring Timothy Spall. "They were definitely a reaction against the monster that The Beach had become." In the process, he went gaga for DV. "We had hidden cameras, and some of them would get kicked by the actors, so you end up with 20 minutes of wasted footage. But that's the spirit of it. It removes all the preciousness. I think DV presents great opportunities for British filmmaking to get a grip of costs. That's why I dislike what Steven Soderbergh has done, using DV for experimental work like Full Frontal: it sends out the message that DV is just a hobby, whereas he reserves celluloid for 'real' movies like Ocean's Eleven."

Boyle retained the medium, and his cinematographer, for 28 Days Later, and it would be hard now to imagine the film without the urgency – and, frequently, the ugliness – that DV brings. "It was so liberating. Everyone had a go. Andrew [Macdonald, Boyle's regular producer] shot some stuff on a roof. I did some bits in my back garden." His single equivocation returns us to commercial matters. "I worry that if people know it's a DV film, they'll just go and see XXX instead."

It would need a bigger man than Danny Boyle to stand in the way of Vin Diesel, but you take the point. Boyle's concern springs from an inherent respect for the audience: plainly, simply, he wants his work to be understood and enjoyed. He is suspicious of personal visions. "They always seem a bit arrogant to me." And he's wary of the term "art house" "There's something undemocratic about a director saying: Here are the tablets, now learn from them. I like to make things difficult but accessible. The extraordinary thing about cinema is that it's a celebration. You get all these people together in a room, and hopefully you connect with them. The trick is getting them there in the first place."

He would know. After all, he did it with Trainspotting. It was the kind of film that it quickly became essential to have seen, in the same way that it is essential to maintain good personal hygiene. "Apparently, they can tell from the first matinée on the first day whether a film's going to be a hit or not. There are usually two people in some cinema in Hamilton on a Friday afternoon. And if there are eight, it's going to be a hit. With Trainspotting, we got those eight people." While it would be easy now to regard 28 Days Later as commercially unpromising, black comedies about heroin addiction hadn't exactly been box-office gold before Trainspotting.

Boyle is currently considering filming Irvine Welsh's Trainspotting sequel, Porno. "People love those characters. And if we can get the boys together again, why not?" He bumped into Ewan McGregor recently, and these erstwhile chums seem to have patched things up: water under The Beach and all that. After lighting up Boyle's first three films (Shallow Grave, Trainspotting, A Life Less Ordinary), McGregor had been poised to play the lead in that film, until DiCaprio expressed an interest. "I think Ewan was very upset by what we did," says Boyle, dropping his gaze to the floor for the first time in our conversation. The room temporarily assumes the air of a headmaster's office. "He feels we betrayed him, and I think he's right." Boyle might have come out of the situation looking like a proper cad, if the likes of George Lucas and Baz Luhrmann hadn't invited McGregor to play with their toys instead. "You have to get in line with everyone else to speak to him now," chuckles Boyle, visibly relieved at not having annihilated his friend's career.

Before Porno gets going, Boyle is trying to launch another project. He's covered murder, drug abuse and a zombie apocalypse, so naturally his next film will be about the euro. Perhaps I don't look excited enough when he tells me, because he is quickly apologising. "It's a lovely script," he protests, "but whenever I say it's about the euro, I see people's faces drop. Oh dear. Empty cinemas everywhere. We may need to introduce some zombies."

'28 Days Later' is released on 1 November