Diane Keaton plays nun in HBO series on pope

We wonder what Sister Mary Ignatius will think of this: Oscar-winner Diane Keaton will play a nun in a coming HBO series that also stars Jude Law as a pope named Larry who's more conservative than...well, probably most of the 266 popes before him.

Don't panic, it's only television.

In fact, it's HBO, partnered with the Britain's Sky and France's Canal Plus, in an eight-episode series, The Young Pope, created and directed by Oscar-winning Italian filmmaker Paolo Sorrentino (The Great Beauty 2013), about the first American pope in history. Shooting on the production begins this week.

Details about when the show will air are not yet available but it's unlikely to be finished by the time the actual current Pope Francis, the first Latin American pope, arrives for a six-day visit to Washington, New York and Philadelphia on Sept. 22.

Which might be a good thing because — did we mention it was from HBO? — there's bound to be at least some sex in it, despite a plot centering on the officially celibate clerics of the Roman Catholic Church.

History shows that precious few popes over the 2,000-year-old history of the papacy actually followed the rule anyway, and if that wasn't always known to most ordinary Catholics, Showtime's The Borgias made it all too deliciously clear in 2011.

Moving on to the casting, or against-type casting, if you prefer: HBO announced Tuesday that Keaton will play Sister Mary, an American nun living in Rome during the papacy of Pope Pius XIII (hmnn, the 13th? Is that a sign?), formerly known as Larry Belardo.

The pope will be played by Law, a two-time Oscar nominee and a Brit with a colorful personal life that includes an ex-wife, five children by three women, and flamboyant relationships with movie stars, models and nannies. Keaton, who's had her own history of affairs with dashing movie co-stars, has settled down lately as a single mom of two kids she adopted in her 50s.

Pope Pius XIII, as conceived by Sorrentino, might not approve of the likes of either, as explained by Sorrentino in a press release.

The young pope is "a complex and conflicted character, so conservative in his choices as to border on obscurantism, yet full of compassion towards the weak and poor. He is a man of great power who is stubbornly resistant to the Vatican courtiers, unconcerned with the implications to his authority."

“No one, even at the Vatican, is prepared for how hard-line this American pope really is,” Tony Grisoni, one of the writers, recently told Variety.

Conflict with the Curia — always good for built-in drama. Also good: family drama. During the series, "Belardo will face losing those closest to him and the constant fear of being abandoned, even by his God. He is however not afraid of undertaking the millennial mission of defending that same God and the world representing Him."

The production has recently been tweeting casting calls for American, British, Irish and North European men over 50 as extras.

Sorrentino engages in a little obscurantism himself in describing what the series is about:

"The clear signs of God’s existence. The clear signs of God’s absence. How faith can be searched for and lost. The greatness of holiness, so great as to be unbearable when you are fighting temptations and when all you can do is to yield to them. The inner struggle between the huge responsibility of the Head of the Catholic Church and the miseries of the simple man that fate (or the Holy Spirit) chose as Pontiff. Finally, how to handle and manipulate power in a state whose dogma and moral imperative is the renunciation of power and selfless love towards one’s neighbor. That is what The Young Pope is about.”

A straight-ahead American trying to find his way in the notoriously twisty corridors of the Vatican? Talk about a fish-out-of-water story.