The parallels between the two renaissance men are unavoidable. Both are polymaths, both multidisciplinarians, both networkers who strive to satisfy their rich and powerful patrons. And yet both are prevaricators, notorious for their flibbertigibbet concentration spans and more interested in starting a project than ensuring its end. Yes, between Leonardo da Vinci and Alan Yentob, the only real difference is that one is a genius and the other is a BBC executive. How appropriate then that Yentob, that great survivor of changing tastes and regimes at Television Centre, should choose Leonardo as his subject now that he has returned to documentary-making as the corporation's "Face of the Arts".
In his three-part Leonardo (7pm, Sundays, BBC1), Yentob unashamedly advertises Leonardo as being, in the words of one hired expert, Dr Sherwin Nuland, "the greatest genius of all time". Yentob is not blind to Leonardo's faults. He extolled the virtues of peace, yet designed instruments of war. He jealously sought to get Michelangelo's great statue of David sidelined. He was the evil Cesare Borgia's chief engineer. Because of his headstrong insistence on painting in oil, his fresco The Last Supper is now no more than a ghost of what it once was.
But his multiple contradictions are another instance of his breadth. Leonardo touched all the bases from art to science: painter, anatomist, optician, central heating engineer, fossil hunter, and madcap designer of diving suits, tanks and flying machines. In the opening episode (27 April), I particularly enjoyed hearing about the daily "to do" list. Things to do might be: construct glasses to see the moon magnified; find out how to install bombards and ramparts by day and night; find out how to square the triangle; analyse the tongue of the woodpecker and describe the jaw of a crocodile. (The list would be unlikely to include: cancel the papers; collect dry-cleaning; cat food.)
Yet the programmes show off Yentob's spatter-gun intellect as much as Leonardo's. They are not traditional TV art criticism conducted by heads talking in front of paintings, although there are plenty of talking heads and paintings around. Nor are they drama documentary, although many scenes are dramatised - with Mark Rylance doing his best to look, at all times, enigmatically intelligent. Sometimes the programmes go into Time Detectives mode. The final programme, for instance, claims that the mystery of the identity of the model for the Mona Lisa has at last been solved: she was Lisa del Gioconda, a revelation only slightly diminished for me when I realised that the same "middle-class housewife" had been fingered by my Everyman Encyclopaedia, published in 1957.
The episode on "The Secret Life of Mona Lisa" is actually the cuckoo in the nest of the series, but may be the best of the pack. It is more like an early Yentob Arena, in which the subject is the iconic importance of the object. Yentob carries a gilt-framed reproduction of the painting on to a Eurostar train and asks passengers to account for her smile. One woman says: "I see a woman who is saying, 'You have got me on the worst day of the month. What am I doing here?'" Another guesses that she is pregnant, which turns out to be Yentob's conclusion, too.
Within each episode is another strand that, knitted together, would have made up a different kind of programme altogether. In this, engineers, enthusiasts and madmen take Leonardo's sketches of sci-fi machines and build them to see if they would work in practice. The results almost beggar belief. With a little bit of creative doodle interpretation, the diving-suit with its compression chamber works and does not fill its wearer's lungs with water; add a tail, and the wings he designed for a man really do transport a stunt pilot through the air; reverse the gears, and Leonardo's sinew-powered tank moves. Most stunningly dangerous of all, a parachutist is attached to one of Leonardo's wigwams and falls from a hot-air balloon hundreds of feet above Africa. We assume he lives.
Yentob rations out these don't-try-this-at-home experiments and cues them in just when the art history risks getting a little dull. Leonardo is bravely scheduled on BBC1 at prime time, but if God did not put the BBC on this earth to make programmes as bright as these available to mass audiences, I don't know what He did have in mind for it.
Used to didgeridoo Rolf Harris's approach to great art, what BBC1 viewers will make of their vole-like host is another matter. Scruffy despite his Armani suits and T-shirts, often waving a cigarillo in his hand, Yentob is not shy about putting himself in the frame. We see him in front of the masterpieces, on train platforms, on hillsides as the flying machines take off, covering half of the Mona Lisa's smile with a paper napkin, and, most comically of all, in the garden of Leonardo's castle in Amboise, where he spent his last years, monkishly scowling over manuscripts in the hope of insight. One day, I trust, Mark Rylance will portray Yentob in a documentary of his life. It will surely hail this eccentric series as the great man's masterpiece.
Andrew Billen is a staff writer on the Times
