“I’m as green as I possibly could be,” declares Jeremy Piven, offering his driving habits as an example. “I’d love to have a huge truck, but I’m not going to,” he says, instead opting for an Audi and an old (’77) Ford Bronco. Piven, best known as talent agent Ari Gold on “Entourage,” returns to TV on March 31 as the title character in the eight-part PBS “Masterpiece” series “Mr. Selfridge,” about the founder of the eponymous London department store.

Adapted by Andrew Davies from a book by Lindy Woodhead, the series follows brash American Selfridge, the marketing genius behind Marshall Field’s department store in Chicago, as he builds and opens Selfridge’s in London in 1909. “He loved P.T. Barnum, and he thought of himself as a performer.  And the store was his theater,” says Piven. “His journey is so fascinating. His life was full and rich and tragic and all those things. So we have a lot to play with.” If it’s successful, another three seasons of episodes are planned.

Piven is also a producer of the series, which attracted him from the moment he read the script. “I hadn’t even finished it when I knew I would jump right in. There was no way that I could say no,” says the Emmy winning actor, for whom shooting in London was a return to the familiar. “I studied Shakespeare at the National Theater of Great Britain, and had a real reverence for the place,” he explains. As for being part of the prestigious “Masterpiece,” Piven likens it to “telling a Jewish mother that you're going to be a doctor.”

Reflecting on his eight seasons of “Entourage,” he says playing Ari “was like the last ten seconds of a round in a boxing match where you give it everything you got. I left it all on the field. After eight years there was some finality to it, even though the ending was open-ended. There’s talk of a movie, which would be wonderful, but I don’t want to get ahead of myself.” Identified as he is with Gold, he says, “Harry Selfridge seems closer to me than Ari. He fancies himself a performer. He’s going over to the U.K. to prove himself. I don’t have to look too far for that.”

But shopping is something about which Piven and his store mogul character diverge. “I think I lack the endurance for shopping that women have,” he opines, adding that most men don’t have the patience required. “We tap out at ten minutes.”