‘Alice & Jack’ co-star Aisling Bea rewrites the rules on supporting character: ‘Quiet, heroic moment’

Aisling Bea’s supporting role in “Alice & Jack” resonates with the Irish-born actress/comedian in its portrayal of a character type often shunted aside on screens big and small.

Not so here.

Bea (“This Way Up,” “Living With Yourself”) plays Lynn, the short-lived wife of Jack (Domhnall Gleeson), whose 15-year on-again/off-again romance with Alice (Andrea Riseborough) provides the central conceit of “Alice & Jack,” a twisty dramedy premiering March 17 on Masterpiece on PBS.

“I think I sort of knew what [series creator] Victor [Levin] was getting at and … one of my passions with my writing and my acting is what is sometimes seen as a ‘side character,'” Bea, 39, told The Post. “Maybe the less dynamic characters that don’t get written about … you imagine them having a whole movie or TV show of their own.”

The series opens with Alice and Jack meeting at a bar and hitting it off. Alice is a successful financial analyst dealing with a childhood trauma, Jack a shy scientist who works in a lab researching rare illnesses.

As their story unfolds, Alice and Jack embark on a 15-year checkered journey that forms the crux of the six-episode series by turns that are dramatic, funny, romantic and heartbreaking.

Lynn enters the picture when she meets Jack during one of his yearslong rebounds from Alice. She gets pregnant and accepts Jack’s marriage proposal, unaware of his deep past with Alice.

Together, Lynn and Jack have a daughter, Cecilia, and all seems good in Lynn’s world … until Alice, once again, reappears in Jack’s life, and he admits to his wife that he’s thought about Alice “100 percent of every day” that they’ve been married.

That’s all Lynn has to hear. She kicks Jack out — ending their marriage then and there.

“I don’t think she thinks she’s too good for Jack but she serves more than the situation,” said Bea. “I don’t know if I’ve seen many of these characters, women who don’t get to be the lead role having a quiet, heroic moment. She says, ‘I’m nobody’s consolation prize,’ ‘I’m nobody’s second choice’ and she doesn’t just say it as a fridge magnet.

“She doesn’t walk away and say, ‘But I actually still love you,'” Bea said. “She’s someone who really knows her own value.”

Bea said her portrayal of Lynn was inspired, in part, by her personal life.

“I have a bit of a dramatic life being in the job that I have, and sometimes I look back at my friends I grew up with who have way less dynamic lives — on the surface. And I’ve seen some of the ways they’ve managed situations that have been thrown at them that are TV-worthy and I’m always like, ‘Nobody writes movies or TV shows about what you guys cope with.’

“They have a beautiful nobility that I don’t think I possess.”

Bea described Lynn as someone who knows her true worth.

“I think she is like the ultimate feminist to walk away [from Jack and her marriage] and not try to fix it,” she said. “That’s modern feminism, to not go, ‘Do you think you should go to therapy and work out why you’re getting involved in this situation?’ No — fix it yourself, it’s not my car crash.

“I like to think [Lynn’s] arc is one that’s very quietly aspirational of how the quiet, less-Instagrammed life has a power and beauty to it,” she said. “And it’s not with a big Shirley Bassey soundtrack in the background but with a few violins, and that’s OK, too.

“I think for a long time these sorts of stories weren’t explored because they were seen as female stories and thus weren’t as interesting or noble or strong or powerful,” she said.

“We weren’t allowed to have bigger lives, but that doesn’t mean they weren’t as interesting or unique — and it’s knowing that those stories are always just as interesting.”