"I originally pitched it to the studio with one line," says Vince Gilligan, the creator of Breaking Bad. "I told them: 'This is a story about a man who transforms himself from Mr Chips into Scarface.'" The line turned out to be a clincher, and it remains as good a description as any of a show that wins serial Emmy awards and is frequently described by fans as being the best drama on TV. It may also be why you're likely never to have seen it.

Breaking Bad stars Bryan Cranston (previously the dad in Malcolm In The Middle) in the Chips/Scarface role. He is Walter White, a high school chemistry teacher suddenly diagnosed with terminal lung cancer. His response to the news is simple: employ his science skills to start cooking the best crystal meth in the south-western United States. The consequences of this single choice soon start to ripple outwards, affecting his family and friends, eventually influencing the actions of some incredibly dangerous people. What results is a drama serial that's humorous, gruesome, compulsive and compelling. It's also a programme that at its core is a morality play, examining what any of us might be capable of given the right incentives.

It's not an easy sell, and Breaking Bad is not always an easy watch. As such it seems to have found itself thrust into the company of other American programmes that have been loved by British fans but buried by broadcasters, from Seinfeld to Arrested Development, Damages to The Wire. Having been bandied around various digital channels, the show has no home on our screens at present, but with the third season being released on DVD, there is now the chance to immerse yourself in a drama that is as idiosyncratic, and as compelling, as Tony Montana taking over a boarding school.

'I wondered why would someone make such a radical change in their lives if they were basically a good person, a non-criminal'

Gilligan, who is 45 but speaks with an avuncular southern drawl that makes him sound 20 years older, made his name working on The X Files. As producer and writer he was responsible for sustaining one of the most successful franchises on TV; a programme where the most outlandish things would happen to ordinary people and be wrapped up in an hour. Then, after nine seasons, The X Files was cancelled. "A year or two after I was still looking for a new gig," Gilligan recalls. "I was talking to a friend and neither of us was having much luck. We were joking around on the phone and he said we should follow the example of a guy who'd put a meth lab in the back of a Winnebago and driven around the south-west. My friend said, 'Why don't we do that?' He was joking, but an image popped into my head of somebody who would do that."

After that conversation, Gilligan began to worry away at the character that would become Walter White. "I wondered why someone like us, which is to say a basically law-abiding citizen, would suddenly do such a thing," he says. "Why would someone make such a radical change in their lives if they were basically a good person, a non-criminal? I think of Breaking Bad as a bit of character study. It's really about this one man and this one particular set of circumstances, the fact he makes decisions that most of us, myself included, would not. We are telling a story of transformation in which a previously good man, through sheer force of will, decides to become a bad man."

The first season of Breaking Bad covered the story of Walter's bizarre life-switch with a tone of macabre farce. Walter and his slacker sidekick Jesse Pinkman (Aaron Paul), a former student, are a source of knockabout laughs, even when melting gangsters in bathtubs filled with acid. As each new season begins, however, both the scale and the stakes of the drama grow greater. Walter's brother-in-law, Hank, a Drug Enforcement Agency official no less, starts to pick up the scent. Mexican drug cartels get wind of Walter's product. What was once played for laughs becomes deadly serious (with the glorious exception of amoral lawyer Saul Goodman, a season two addition and cult figure in his own right).

Walter wanders deeper into a world of which he previously knew nothing, deeper into immorality, but as the viewer you are always able to understand why he's doing it. The same goes for the reactions of his friends and family. The meticulous plotting and characterisation (as well as stand-out performances from Cranston and Aaron Paul, who between them have won four acting Emmys on the show) is what raises Breaking Bad above most, if not all, contemporary TV dramas. And it's here that Gilligan built on his X Files experience.

'I thought: Let's have every action have its consequences. Let's revisit tiny moments from past seasons and see if we can milk more drama from out of them'

"To crib a bit of Walt's expertise, it is very important to us that every action have a reaction, be it chemical or physical," Gilligan says. "In real life, actions have consequences and when bad things happen, big or little, they tend to resonate with us. We'll think of something that was said in a careless, thoughtless moment years before and we'll stew on it. I've grown up watching a lot of television, more hours of it than I care to admit to, but one thing that I've noted as a consumer is that things don't tend to resonate on a TV show. Marshal Dillon will gun down a bad guy in the middle of Dodge City one week and by the next it's completely forgotten about. Luckily I've never killed anybody, but I'd have to think that it would stay with you, unless you were an ice-cold sociopath. I'd have to think that pulling the trigger and killing someone would haunt you for the rest of your days. That's not what's portrayed on TV normally." Through the serial nature of his drama, Gilligan saw an opportunity to correct this. "I thought, let's have every action have its consequences. Let's revisit tiny moments from past seasons and see if we can milk more drama from out of them."

To achieve that effect requires many hours, often talking in code. "I am blessed to have six very talented writers, most of whom have been with me right from day one," says Gilligan. "We all have a shorthand for talking about things that happened in prior episodes and this allows us to remember moments we can mine for further use. We ask ourselves the same questions over and over again, like a mantra. 'Where is Walt's head at right now? Where is he coming from? What is his fear, what was his hope?' I won't lie and say we don't work towards certain ideas we have, but our best work is when we don't think about the future too much and we think about the now. That's when some of our best moments have come to us, usually after many, many hours of frustration. I want our show to feel as real as possible and I want those moments of reality to feel earned."

This maxim applies to the violence in the show too, a visceral kind that can easily disturb (think of Tony Soprano in a moment of fury, add the deliberate application of chemical properties, and you're pretty much there). "Breaking Bad is not a show for everybody and it was never intended to be," says Gilligan. "When you live that kind of life and you choose to become a criminal, bad things are going to happen. We never shy away from violence on this show. We never revel in it in any sort of gleeful or nihilistic sense; but, on the other hand, we want to be clear-eyed and realistic about these choices Walter has made and this world he's forced himself into."

Gilligan is true to his word about his commitment to verisimilitude. However, there are great moments of unreality in Breaking Bad, too. The show has visual flair: its time-lapse and POV sequences (often those of inanimate objects) are the subject of YouTube tribute. There are also moments of absurdity, such as the opening scene of one episode in season two where the normal introductory teaser is replaced by narcocorrido music: ballads that sing the praise of drug dealers. And did I mention "Better Call" Saul Goodman? It may require a strong stomach, but Breaking Bad also rewards a thoughtful mind. And watching it might keep you from loading up a caravan and heading out on the road.