In an early scene of the new drama Utopia, shown on Britain television, an academic rejects a student's proposal for a PhD on conspiracy theories with the clincher: ''I mean, conspiracies aren't very now, are they?'' The line is winking inwardly because Utopia is the second conspiracy thriller in a row on the network, Channel 4, following Secret State - with a third, Complicit, soon to come.
So conspiracies are very now, and about to become even more so with the return of the genre's dark lord and author of the bible of the form, The Da Vinci Code. Dan Brown revealed last week that his new novel, Inferno, would be published on May 14.
Having thwarted the Catholic Church's cover-up of Jesus Christ's sex life in The Da Vinci Code and a centuries-deep web of Freemasonry in The Lost Symbol, Brown's protagonist, Robert Langdon, will now follow the trail of Dante's Inferno into a ''harrowing world'' filled with secrets and mysteries. Although we aren't yet allowed to know Brown's narrative, Dante's is in the public domain and we may surmise from it that Langdon will face successive challenges representing heaven, hell and purgatory.
Although Brown's books frequently present religion as an agent of conspiracy, his literary career has benefited from a general Western decline in faith. The human instinct to see a shape to our days, which once drove people to the Bible and Dante's Inferno, now sends them to The Da Vinci Code and Brown's Inferno. In frightened, sceptical times, conspiracy theories flourish.
And those who question official histories have recently received vindication. While no truth has ever been proved in the favourite fantasies of conspiracy theorists - that, for example, the Apollo moon landings were faked, Princess Diana was murdered or President Barack Obama is not an American - numerous grave conspiracies have been exposed.
The activities of British TV presenter and paedophile Jimmy Savile benefited from at the very least a conspiracy of silence in the circles in which he moved. At a lesser level of human suffering, it is now established that cabals existed in the banking sector to fix the Libor lending rate. And who knows what secret deals may be revealed by the British government's inquiry into the Iraq war if (after a delay that is itself the subject of conspiracy theories) it is eventually published?
We also now know that the private lives of the well known and those thrown into the news by tragedy routinely suffered intrusion from a conspiracy of journalists. There was indeed, as writers and readers of conspiracy fiction frequently warn, another story behind the official story.
Brown brilliantly anticipated the mindset of the 21st century, in which citizens would come to suspect that every stone had something hidden under it and would be justified in their suspicion by progressive revelations. But Brown's mistake was to suggest that conspiracies involve medieval sects searching for mystical chalices. As we have discovered in a series of official reports, these are indeed conspiratorial times, but the collusions and cover-ups take place not among hooded figures in crypts but between police officers and amid bankers, politicians and journalists. And, indeed, priests. As it happens, the Vatican, a recurrent villain in Brown's books, was involved in a cover-up, although it was trying to hide not the sexuality of Christ but the paedophilia of some priests. The biggest conspiracies are found not in fiction about the far past, but in the facts of the present.
Mark Lawson is a columnist, feature writer and theatre critic for Britain's Guardian newspaper.