When Jude Law first read the script for HBO’s The Young Pope, he was unsure if viewers would take to the rancorous, thin-skinned and ultra-conservative leader he portrays.

“My one concern early on was, ‘Could this be conceived as far-fetched?’” Law says. “But now,” with Donald Trump taking office next week, “it seems totally plausible.”

Many parallels can be drawn between the future US president and Law’s character on The Young Pope, a present-day American cardinal named Lenny Belardo who has been tapped to become the next pontiff. When he arrives in Vatican City at the start of the 10-episode series, Lenny – now known as Pope Pius XIII – is considered a blank slate onto which older cardinals can push their own ideals. So it comes as a shock when he reveals himself to be the most audacious, radical pope yet: a homophobe who refuses to show his face in public and may not even believe in God.

Lenny is “unpredictable and unknown in that environment, just as Trump is in the political world”, Law says. “And I think just the impact and the surprise in his election is perhaps relatable.”

The Young Pope was created by Italian filmmaker Paolo Sorrentino, whose surreal 2013 drama The Great Beauty won an Oscar for best foreign-language film. The idea for the show – which was co-produced with Sky Atlantic and Canal +, and has already aired in Europe – stemmed from his desire to explore the inner workings of the Vatican.

“On the one hand, it’s very close to [Italians], because we live nearby and see it every day,” says Sorrentino. “On the other hand, it’s very far, because it’s very inaccessible and mysterious.” He wanted to create a Bishop of Rome who was “unprecedented: a pope who would be the complete opposite from the pope we currently have”, Sorrentino says of Pope Francis, whom he considers to be more liberal than Pius XIII.

For Law, 44, the challenge was humanising the caustic, chain-smoking pontiff, who still bears the emotional wounds of being orphaned as a child and now spews blistering insults at everyone in his path, including the nun (Diane Keaton) who raised him and his former mentor (James Cromwell).

“To understand who he was, I created an airtight sense of what his childhood was, how he survived in the world without parents and the skills he established to get him so far,” Law says. As Lenny’s backstory in early episodes suggests, “faith became his closest ally. He was a very good student of God and was always encouraged to be very dogmatic” – to the point of being extremely literal in his understanding of the Bible.

The British actor doesn’t consider himself religious, although his mother was raised a Baptist. She “brought us up in a very moral environment, and I’ve always been curious about faith”, Law says. “I read about and question it in myself daily, and working on this only heightened that.”

Sorrentino – who shot The Young Pope in Rome and other locations over seven months – says he has yet to receive any response from the Vatican or backlash from religious groups. He’s now writing a second season of the show, but jokingly insists that it hasn’t had any impact on his own beliefs.