Surprisingly it tore out of the cult cinemas and became a bonafide mainstream hit. Which meant only one thing: a sequel was imminent.

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Producer Andrew Macdonald, who worked alongside Boyle and writer Alex Garland on the original, picks up the story: "We saw an opportunity to make a second film that already had a built in audience. We thought it would be a great idea to try and satisfy that audience again. The hard bit was to try and find a story which would live up to the power and depth that Danny and Alex brought to the first film.”

The first decision the filmmakers had to make was when should the sequel be set. Should the film involve the original cast? Should it go further into the future? Should it be a prequel? '28 Days Later' told the story of a virus unleashed following a raid on a primate research facility by animal rights activists. Transmittable in a single drop of blood, the virus locks those infected into a permanent state of murderous rage. Within 28 days the country was overwhelmed and a handful of survivors desperately struggled to salvage a future.

“Alex came up with a lot of ideas and eventually we agreed upon a concept about what would happen to the UK after the disease had been eradicated and the quarantine was lifted,” explains Macdonald. “What would happen if there were only 500 people populating the UK? Who would be there to organise the survivors and refugees coming back from overseas, and what would happen to the Brits who survived? All those questions seemed interesting to us and it was out of them that the story evolved”.

With Boyle, Macdonald and Garland (who have credits like 'Trainspotting' on their collective CV) working on the existentialism-in-space movie 'Sunshine', the search began for a talented young director who would have the flare to follow in Boyle’s footsteps as well as be able to bring a fresh new perspective and their own unique vision to the film.

“We were looking for a filmmaker of some individuality who could bring something different to the film,” says Boyle. “London was such a big part of the first film we thought that getting somebody from outside the UK to come in and direct would be an interesting approach as they would give the Capital a fresh look.”

Boyle had recently seen the provocative thriller 'Intacto', the feature film debut from Spanish director Juan Carlos Fresnadillo which had been a huge international and critical success. “I thought Intacto was amazing,” recalls Boyle. “A terrific thriller with tremendous flare and energy, as well as being a highly individual piece of filmmaking."

After seeing Intacto Macdonald and Garland were also convinced that Fresnadillo was the director they were looking for, and the filmmakers approached him. They were thrilled when Fresnadillo and his Spanish producing partner Enrique López-Lavigne agreed to come on board.

Fresnadillo and López-Lavigne began working on the script with the help of Spanish screenwriter Jesus Olmo, developing the story around a family and what happened to them in the aftermath of the original film. López-Lavigne explains: “The family was a good idea for us, and we wanted to develop this into something. But there is always a problem with this kind of structure in which you are looking at the new world through four different eyes, instead of one. That's why we had to find a really strong concept for the actual storyline. And what we came up with is a storyline, that we really believe; it’s about the idea that no one is unaffected from his past.”

With the script complete, the casting process had to get underway. The challenge of the casting process was to find the central family who needed to be a believable and realistic unit around which the extraordinary events of the story evolve. To play Don, the filmmakers nabbed 'The Full Monty' and 'Trainspotting' star Robert Carlyle.

“Don has been project manager on building sites and self-builds," explains the actor. "During the original outbreak his children were in Spain on holiday. He manages to survive the beginning of the first 28 days along with his wife, and they take shelter in a cottage in the country. But that does not last for too long before the infected come knocking. He manages to escape, leaving his wife to her fate. “

For the mother of the family, Alice, Fresnadillo turned to Catherine McCormack (Braveheart). And with Don and Alice cast, the next character to find was their 12 year old son, Andy. The story requires the character of Andy to grow up fast as he has to survive the devastating events of the outbreak of the virus whilst unbeknownst to him, he may hold the key to its cure.

After seeing some 600 children, the film-makers discovered Mackintosh Muggleton. "He delivers in the story this unique feeling, and especially that feeling about the curse," explains Fresnadillo. "His family is completely cursed. So, we needed somebody like Mackintosh who could play this kind of kid [who is] absolutely overwhelmed in the situation, but at the same time he is trying to make his best in this new world.”

With the family finally cast the filmmakers focused their attention on the four Americans who would play the supporting roles.

Australian actress Rose Byrne was chosen as the medical officer Scarlet: “My character is a military doctor and she is stationed with the American army as they quarantine Britain. She is very assertive and smart, but she is also a bit of a renegade in terms of defying the army and the codes.”

She's joined by Jeremy Renner, who is best known for his portrayal of the serial killer Jeffrey Dahmer in 2002’s 'Dahmer', was cast as the Special Forces sniper Doyle; Harold Perrineau ('The Matrix Trilogy', 'Lost') as the special forces helicopter pilot Flynn; and Idris Elba ('The Wire') as General Stone, the US General in charge of the re-population of the UK.

Renner plays a Special Forces sniper whose duty is to keep watch on the rooftop to keep District One safe. When the outbreak occurs, he is given gut-wrenching orders to indiscriminately take out targets, including woman and children. Morally conflicted, Doyle can't carry out the orders and deserts his post. Once rogue he heads off on his own heroic mission to save the lives of a group of civilians, which include Andy and Tammy.

As with the first film, '28 Weeks Later' is almost entirely set in London, but this time the filmmakers have upped the ante on the action-thriller elements and created a story on a considerably larger scale than 28 Days Later.

“We return to the deserted London in which the first film was set. Over six months has passed and this time we find the authorities are trying to restructure and clean up the capital. Get it back on its feet,” explains producer Andrew Macdonald.

Helping Fresnadillo find his feet in London were Boyle and Garland: “Obviously, I asked for help from Danny and Alex Garland, because I didn't know too much about the city, and it was my first experience in shooting a movie in a language that is not mine. Danny Boyle’s vision for me was really important because he, in a way, is the mother of this creature, and if you want to make another movie around that, you need his help. So, I worked in a very freestyle way, but with the legacy of Danny,” he explains.

“The main challenge for me was to make this story real," he adds. I put myself [in the place of the] audience watching the movie, and knew that I would love to see a movie [in which] you could smell the characters and the environment, and you could feel that story could happen really close to you. That’s why I made the movie as kind of a horror documentary…[by doing it that way] it’s delivering something and conveying something real about the story. On the other hand, it’s difficult to shoot in that way. You need a lot of cameras. Handheld style. And, especially the acting and the art department, and everything need to be linked to that idea. So, it’s unusual, but at the same time I think it’s the best way that you can face this story.”

And that story might not be as far-fetched as it seems. With outbreaks of bird flu, mad cow disease, SARS, and the West Nile virus in recent years, the idea of an infectious disease wiping out an entire city, or even country is not entirely out of the question. In '28 Weeks Later', the story focuses on how an urban environment like London might be affected, and how the government might respond to the daunting task of containing an outbreak.

Producer Allon Reich explains: “What I hope we do with this film is go, ‘well, what if a virus like this happened? The next step would probably be quarantine. And then, at some point, it would probably be a US-led force that would try and slowly repopulate the country. Well, what would that feel like?”

He continues to discuss how the population might respond: “If you’re faced with a situation that you have to deal with… somehow from the ashes of what looks like an impossible situation, civilization and people’s strength and willpower emerge again. And I think what you come into in this world, is exactly that: a sort of determination from people to rebuild their country.”

Before '28 Days Later', who'd have thought a zombie movie could have so much meat on its bones…