Don’t expect Alfie Allen to play a nice guy anytime soon.

In “Plastic,” out Friday, the Londoner portrays Yatesy, the roughest in a gang of four lads who stage a diamond heist.

In next month’s “John Wick,” he plays the son of a Russian mobster. Keanu Reeves stars as the titular character, a former assassin pursuing a more peaceful life until Allen’s character kills his beloved dog in a robbery gone awry.

It’s fun playing the bad guy … It comes naturally.

 - Alfie AllenAnd, when “Game of Thrones” returns next year, Allen will resume his role as Theon Greyjoy, who betrayed the Stark family in a power grab — only to be betrayed by his men, taken hostage, tortured and turned into a slave called Reek.

“It’s fun playing the bad guy,” Allen tells The Post. “It comes naturally.”

It certainly seems that way. With his cutting cheekbones and icy blue eyes, Allen, 28, has an aura of danger and mischief — and the family background to back it up.

His father is famously boozy British comedian Keith Allen, while his older sister is brash singer Lily Allen. Like his dad and sister before him, he was kicked out of various schools growing up.

“I wasn’t expelled for anything vicious, just being cheeky, not doing what I was told … rising to the bait if someone said something annoying about my dad,” Allen told the Daily Mail in 2008.

He says going to a boot camp in Fort Lauderdale, Fla., when he was 12 helped him get it together.

His sister, though, might disagree. Her 2007 debut featured a track called “Alfie” with the lyrics: “My little brother’s in his bedroom smoking weed ... Get off your lazy arse/Alfie please use your brain.”

In “Plastic,” the actor has even harder edges than usual, thanks to bleached-blond hair.

“I was a bit dubious at first,” he says of the dye job. Director Julian Gilby had to convince him it was right for his character.

The film is loosely based on the true story of a group of Manchester boys who managed to steal more than $3 million in gems from a Beverly Hills jeweler by posing as a prince and his staffers. The gang hired a private jet — paid for with a stolen credit card — to fly the jewels and jeweler to London. Upon landing, the envoy was shuffled into limos, and the gang’s leader drove off with the jewels.

In “Plastic,” the store is in Miami, and Allen enjoyed hanging out in Florida with his co-stars: Ed Speleers from “Downton Abbey,” Will Poulter from “We’re the Millers” and Sebastian De Souza from “Skins.”

“We all got along famously,” says Allen, who declines to talk about his personal life but reportedly split with actress Jaime Winstone in July and has since been rumored to be involved with Anna Kendrick.

The guys have a lively on-screen chemistry. Just as watching “Oceans 11” conveys the vibe that George and Brad were having a good time when the cameras weren’t rolling, so it is with this heist flick.

But Allen insists he didn’t get into any more trouble than karaoke-ing Dr. Dre in the hotel bar. “I’m definitely not a bad guy in real life,” he says with a sarcastic chuckle. “I’m really lovely and sensitive.”

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