As Poppy, a 30-year-old London schoolteacher who is the ray of sunshine at the center of Mike Leigh’s “Happy-Go-Lucky,” Sally Hawkins emerges as a valiant figure in a harsh landscape. “She’s so much more than the happy-go-lucky persona she puts out. I learned a great deal from her,” says this grad of the Royal Academy of the Dramatic Arts. “Poppy has incredible depth that is not noticeable at first glance, but by the end, I hope it’s apparent.”

Leigh spotted Hawkins’ potential early. In 2002, she made her film debut as a chirpy tart in his “All or Nothing” and played a stifled aristocrat in his “Vera Drake” in 2005.

Like her current onscreen persona, Hawkins seems genuinely upbeat — even with her left arm in a sling after an on-set accident broke her collarbone.

“I had to have it pinned and I’ve been wrapped up in cotton rolls and treated like royalty ever since. I’m not cornering the market in happy,” she jokes — Poppy-like.