CONSIDERED SIMPLY as popular entertainment, which gives more pleasure? The creation of a spine-tingling, hair-on-the-back-of-the-neck-raising myth, dripping with ancient secrets, hidden codes and arcane but murderous conspiracies? Or the satisfying pop as a myth like that is punctured? It must be a close call.

Dan Brown’s bestselling novel (and we must stress the word “novel” here) The Da Vinci Code has been a top-of-the-range, leather seats and walnut-trim example of just such a myth, given added frisson by his claim that key elements of this para-Christian yarn are based in historical fact.

Last night The Real Da Vinci Code (Channel 4) brought us the satisfying pop, with Tony Robinson approaching the task with the painstaking relish of a teenager bursting a particularly large and offensive zit. His restrained yet systematic pleasure in the work in hand was a joy to behold.

Old TAFKAB (The Artist Formerly Known As Baldric), has carved a useful little niche for himself by representing the ordinary little guy investigating the wacky world of archaeology and social history. In early editions of Time Team, no doubt prompted by over-eager directors, he used to scurry across muddy fields like a Jack Russell that had accidentally swallowed its master’s stash of amphetamines.

Even then it was always apparent, somehow, that this image disguised a rather serious man, politically active and committed, and genuinely fascinated by history. Lately the schtick has mellowed. He is much less frantic, and more interested in explaining. Last night, while still playing the innocent Everyman at large, he was in danger of seeming downright authoritative.

In fact The Da Vinci Code is only a reworking of that 23-year-old spine-tingler, The Holy Blood and the Holy Grail, so Robinson was popping two zits at once. The thesis of both books, if you have somehow managed to escape it, is that Jesus survived the Crucifixion, married Mary Magdalene and had a child, who was then taken to southern France, where his or her descendants eventually became part of the Merovingian dynasty of French kings.

Encoded documents proving this were found by a local priest in a hollow Visigothic pillar during renovation work at his church in Rennes-le-Château, in the Languedoc. The Holy Grail, it seems, refers not to the cup used at the Last Supper, but, by a linguistic trick of medieval French, to this holy blood-line. The secret has been protected for centuries by a shadowy organisation called “The Priory of Sion” whose Grand Masters have included Leonardo da Vinci, Sir Isaac Newton and Jean Cocteau.

There’s lots of other guff too, about the Knights Templar excavating Solomon’s Temple and Cathar heretics spiriting away a mysterious treasure before their last bastion surrendered. The authors of The Holy Blood and the Holy Grail interviewed a rather peculiar-looking Frenchman called Plantard who claimed to be Grand Master of the priory and a descendant of J. C. himself.

Even though I visited Rennes-leChâteau in 1981, the first book never really did it for me. There was too much wild speculation presented as overwhelming probabilities, too much “sleight of logic” used to build this improbable house of cards.

Anyway, if Jesus ran off with Mary Magdalene and had a family, he wouldn’t really be the same Jesus any more, would he? And the fact that a rather peculiar elderly Frenchman was claiming direct descent wouldn’t mean much. He would still be a rather peculiar elderly Frenchman. No doubt, in time, some form of genetic tracking will prove that millions of us are directly descended from King Nebuchadnezzar of Babylon, even Robert Kilroy-Silk — especially Robert Kilroy-Silk, come to think of it — but we will all still remain stubbornly who we are.

Anyway, Robinson established, with meticulous care and fair-mindedness, that The Da Vinci Code is all a load of bunk, carefully demolishing each element as he went along. The killer was the revelation that the Priory of Sion was a hoax invented for a laugh by a group of French surrealist bohemians. Robinson’s interview with the Holy Blood co-author, Michael Baigent, was particularly excruciating, as the writer struggled to preserve the credibility that keeps his book selling. Pass the Clearasil.

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