The Genius of British Art, David Starkey, Channel 4

“Henry VIII is the only king whose shape we remember,” David Starkey tells us in the first of a new series of “polemical essays” on British art. To demonstrate, he reduces the king’s form to its bare Cubist geometry. He sketches a trapezoid for the chest – an impressive 54 inches in life, as attested by his made-to-measure suit of armour; two “chicken-wing” triangles for the puffed sleeves; two simple parallel lines for the wide-apart legs. Oh, and a small, inverted triangle for the codpiece. This last addition, as originally drawn-in for comedic value by the Tudor historian G R Elton, and fondly recalled, never failed to raise a titter amongst the callow students of Dr Starkey’s Cambridge undergraduate days.

The famous Henry VIII form, is, of course, handed down to us through Holbein, a painter, Starkey suggests, who “invented” the portrait. This actually isn’t true, but, as this is a biased, impassioned polemic, we’ll let it pass. In any case, Starkey doesn’t actually say it was Holbein, but rather that, “The Tudors invented the portrait.” But as Holbein was Henry VIII's official painter, this more or less amounts to the same thing. And, being an impassioned scholar of the period, Starkey niftily side-stepping the Italian Renaissance clearly isn’t going to make him lose any sleep.

But Starkey doesn’t ignore the Italians completely – Henry, after all, wanted to embody, through his portrait, the magisterial power and authority of Rome. He therefore looked at what Pope Julius II – who was patron to Michelangelo and then Raphael - had achieved in PR terms and wanted the same. And as Henry sought to build a new Rome in England’s green and pleasant land, a new English Bible was sent by royal decree to every parish in England. As the self-proclaimed sole intermediary between God and man, the Bible’s woodcut frontispiece shows the king receiving the scriptures directly from Christ. With the earthly king’s vast bulk occupying his splendid throne, the diminished Christ appears like some lackey civil servant handing over a few forms for official rubber-stamping.

These images of power and propaganda created, says Starkey, an image of England that was to endure, and Holbein, let’s face it - genius notwithstanding - had great material to work with. Van Dyck, on the other hand, didn’t, and had to invest all sense of power and majesty in a horse, on which the puny Charles I was mounted. This suggested physical stature where stature was clearly lacking. The Flemish painter was gifted at such visual trickery and his portraits of the ill-fated king were swaggeringly theatrical affairs, in stark contrast to the austere portaits painted by his earlier, German counterpart.

Yet, if we are to believe Starkey, divinity was also on Van Dyck’s mind when he painted Charles in a triple, quarter-length portrait. This “holy trinity” of heads, with Charles apparently taking the part of Christ, was, in fact, simply an attempt to show Charles in “the round” - profile, semi-profile and full-face – so that Bernini could complete a commission for a bust without Charles actually leaving England to sit for him.

As a historian Starkey is terrifically persuasive, but as an art historian he definitely plays fast and loose with his subject (take his fruity description of a pomegranate, its “labia-like flesh” suggesting the “sexual ripeness” of the Virgin Queen). And when he tackles matters more contemporary our faith in him wavers just that little bit more. Moving on to the age of Diana he tries to convince us that the late Princess of Wales had newspaper headline writers under her full command by some kind of intimate telepathy. It’s certainly true that Mario Testino made her look every inch the divine goddess, but even her powers of media manipulation weren’t as mighty as Starkey claims.

• Watch The Genius of British Art on 4oD