The Borgias (Sky Atlantic)

Rachel Cooke winces at Jeremy Irons’s hammy performance as a pope.

Crikey. What fun it is that Jeremy Irons is playing the 15th-century pope Alexander VI in Showtime's The Borgias (Saturdays, 9pm). Apart from anything else, he has marked the occasion of its British launch by giving an interview to the Radio Times, an encounter that could not be more hilarious if it tried. (Sample sentence: "I have a fantastic priest in Ireland, although I'm not a Catholic . . . I go to church if I want to say hello to the community.")

Not only do we learn that the castle-owning Irons, who considers himself a perennial outsider, toyed with the idea of becoming a gypsy after leaving Sherborne public school. We also discover just how seriously he is taking this particular role.

“A danger with television is that viewers always want outrageous licentiousness," he says, as though The Borgias would be entirely about frescos, Vatican politics and canon law, were it not for us pesky box-watchers.

On screen, Irons is even more pompous, if anything, by which I mean so thoroughly hammy that he deserves to be tossed straight on to the nearest barbecue.

It's not just the fluttering of his hands, a tic that enables him to flaunt his giant papal rings (they look a bit Accessorize to me, but he obviously loves them), or the loopy, ecstatic look that he flashes the swooning crowd as the papal tiara is lowered on to his head. No, what really drives you mad after a while is how he seems always to be on the verge of tears. As I understand it, Pope Alexander VI was an enormously fat good-time boy with a nasty sideline in wanton poisoning - "a mitred ape", according to the cardinals whom he beat to the job - not some rake-thin, world-weary, trembling milksop. Irons, however, will emote. I guess it makes him feel like he's doing Shakespeare, not panto - but panto this most definitely is.

Neil Jordan, its writer and director, should be ashamed of himself. My dear, the dialogue: coy, cheesy, replete with anachronisms. It's as
if Dan Brown had watched The Tudors and thought, I can do this kind of thing.

“There was nothing ecclesiastical about you last night," says a nameless naked female to Cesare Borgia (François Arnaud) as he pulls back on his bishop's robes. "My kind? I don't have a kind and nor, I suspect, do you," says Michel­etto Corella (Sean Harris), a baddie, if you hadn't guessed, to his new master (Cesare again; he does get about).

There is much talk of flagellation, be it with leather whips (Cesare to Micheletto) or silk rope (Giulia Farnese to herself; she has aborted her child and this is her penance). In panto, characters shout: "He's behind you!" In The Borgias, Derek Jacobi, who plays - until he is poisoned - another cardinal, shouts: "Simony!" (Frankie Howerd, how we miss you.)

Most of the action seems to take place in semi-darkness, possibly to compensate for the sets that, although they don't wobble, feel strangely old-fashioned (think Liz Taylor in Cleopatra on a budget).

As a result, it took me a while to work out whether there was a single performance worth praising. There is one. Simon McBurney's turn as Johannes Burchart, a priest whose expertise in canon law is extensive enough to provide more or less any precedent the new pope should require - believe me, the boundary commission ain't got nothing on Alexander's plans for the college of cardinals - isn't bad.

What's more, I detect about the corners of his mouth the beginnings of a smile whenever he appears in a scene with Irons. Is McBurney fighting the temptation to giggle? I hope so. Even if this is not the case, it will be true soon, surely. For it gets ever more ridiculous from here. The murderous Cesare, desperate to protect his father's interests, will grow ever more nasty. His sister, the sweet and almost albino Lucrezia (Holliday Grainger), will grow ever more creepy. And his daddy-o, the Holy Father, will grow ever more randy.

So far, we have not glimpsed Jeremy's bobbing naked backside. It can't be long, can it? The Borgias' beds, I have noticed, are amply supplied with gauzy drapes. I fancy his silhouetted botty will take a starring role yet.