Only the assassination of JFK has generated more conspiracy theories than the character of Cigarette Smoking Man in The X-Files. In the impossibly culty series about the paranormal, he has unspecified links with the Department of Defence, FBI, CIA, NSA and the murky Syndicate. This shadowy figure is also suspected of having had an affair with Mulder's mother and of being his real father - to say nothing of his alleged involvement in the killing of JFK.
Cigarette Smoking Man - also known as Cancer Man - is regularly voted The Nastiest Villain on Television in polls. To prove the point, he commits what is surely the most heinous crime in America: he defiantly smokes in No Smoking areas. He is forever jousting with the two upstanding agents. "You can't protect the public by lying to them," complains Mulder in one classic exchange. "It's done every day," replies Cigarette Smoking Man, typically shrouded in darkness. "I won't be a party to it," snaps back Mulder. "You're a party to it already," Cigarette Smoking Man says insinuatingly. "What's the truth, Agent Mulder?"
The man who plays him, how-ever, couldn't be nicer. William B Davis is an urbane, middle-aged man in a natty blue suit, sipping tea surrounded by pot plants in a civilised central London hotel. Impeccably well-mannered, he is the soul of sophistication. He even abhors smoking.
He had a blue-blooded training. Schooled at LAMDA, the Canadian actor was employed in the 1960s as an assistant director under Laurence Olivier at the National Theatre, where he worked on Miss Julie with Maggie Smith.
As befits a philosophy graduate, he has a suitably complex explanation for the late 20th-century fascination with conspiracy theories. The sheer weight of data we have access to in the electronic era, he argues, "has led to insecurity about information - which is odd when we have so much more of it. It has opened up the possibility of believing in lots of different things at the same time, and the proliferation of conspiracies.
But what is it about Cigarette Smoking Man - or "CSM" as Davis affectionately calls him - that chimes so well with this millennial sense of insecurity? "He embodies the ambiguity and danger that goes with smoke," Davis asserts. "The smoke imagery means you can't quite pin him down. It gives him an aura of mystery because you can see him less clearly. It's also a metaphor for Lucifer."
The role has prompted no complaints from the famously vigilant US anti- smoking lobby, but, according to Davis, "it has attracted vociferous protests from the pro-smokers, who claim CSM is presenting smoking in a bad light. I'm quite relaxed about that," he adds with a laugh.
After CSM, Davis is wary of being typecast as a villain. "That's a concern," he admits, "but it works both ways because I now have many more casting directors calling me."
For the time being, though, most of Davis's energies are devoted to the continuing power struggle between CSM and Mulder and Scully. (In his odd spare moment, Davis works on maintaining his position as his age-group's Canadian National Water-skiing Champion - I kid you not.) "At a mythic level, the relationships in The X-Files are black and white," Davis reckons. "You can work out the archetypal Jungian references - Scully is the virgin hunter, Mulder is the hero and CSM is the Devil. On a more psychological level, there are similarities between Mulder and CSM. They are both fanatics who have sacrificed their personal lives for the cause, there is a grudging respect between them and, of course, they might be related."
But, just what is it that draws X-Philes from around the world in their millions to the programme - and all the related paraphernalia of websites, conventions and book-signings? "As an existentialist, I think what people have to do is create a meaning for their lives," Davis muses. "If that meaning comes from The X-Files or dog shows, that doesn't matter. As long as it's successfully giving them meaning, then it's fine."
'Redux', the new X-Files video, released by Fox, is now available in the shops, pounds 14.99. 'The X-Files' continues on Sky 1 on Sundays and on BBC1 on Wednesdays.