Now another major chunk of dodgy faction is about to be rolled out in cinemas across the world - yes, it's The Da Vinci Code. The film's source, Dan Brown's multi-million-selling thriller, is choc-a-bloc with seriously untrue "facts" about Christianity. How, I wondered, are readers reacting to these fictions? I compiled a questionnaire and buttonholed 100 strangers, friends and colleagues.
I didn't bother asking about Brown's obvious howlers: the claims that the early Church was run from the Vatican, or that Wagner was a Freemason. And I certainly didn't ask if St John in The Last Supper was really Mary Magdalene; Leonardo is notorious for painting androgynous saints - try Googling for his Baptist.
But how about the "fact" in Brown's preface that the Priory of Sion is a European secret society founded in 1099? My fears were justified: 39 of the people I asked believed that. They didn't know that the Priory was invented by a couple of Frenchmen and registered on May 7, 1956.
Then the compass shifted: only nine believed the idea that Jesus married Mary Magdalene and that their descendants became kings of France; only 11 that "the Holy Grail" is a coded reference to this claim; only eight that the Priory possesses Magdalene's account of her time with Jesus; only six that she's buried under the Louvre's glass pyramid.
So far, so reassuring. Then a shock - 43 readers believed that the Roman Catholic Church burned five million women at the stake because they were witches. Five million women? True, another 18 suspected the figure might be high. It was: the current estimate is that the total killed in Catholic and Protestant countries was between fifty and one hundred thousand; terrible enough, but nowhere near Brown's fantasy figure.
Next, the notion that for the first 300 years Christians believed that Jesus was only a man and not divine. Half my respondents ticked this one, unaware that St John and St Paul, superstar leader-writers of the first-century Church, proclaimed in the most spectacular fashion that Jesus was God.