A return engagement is in the stars for Broderick and Lonergan

Nearly 40 years later, the best friends — who had met at 15 in a school up the street — are still talking about that class, taught by a man Lonergan described as “very quiet, very sincere, very gentle.”

“He kind of stuck in my mind,” Lonergan, who went on to a celebrated career as a playwright and screenwriter, said. “I thought he’d be a good character in a play, and the astronomy classroom at the planetarium would be a great setting.”

Broderick added: “We imagined a whole life for this teacher.”

In 2009, Lonergan unveiled “The Starry Messenger,” a sweetly comic drama about a middle-aged astronomy instructor, mired in the minutiae of marriage and career, who looks to the heavens for guidance. And he cast Broderick as Mark Williams, its lead.

It was to be the playwright’s highly anticipated return to the stage, after a move into moviemaking that peaked with the Oscar-nominated “You Can Count on Me” but ran into legal drama over the fate of its follow-up, “Margaret.”

News reports at the time warned that the New Group production was doomed — that Lonergan was overwhelmed by his first efforts at directing his own unwieldy play, that Broderick couldn’t remember his lines.

But others came to see redemption when the play opened. “If this is what a disaster looks like, bring on the apocalypse,” Ben Brantley wrote in The New York Times, contending that Broderick had delivered “his finest, most affecting performance in years.”

A decade later, “The Starry Messenger” and Broderick have arrived in the West End of London, directed by Sam Yates and co-starring Elizabeth McGovern as Mark’s wife.

In separate interviews — Broderick in London before a rehearsal in early May, and Lonergan in New York on the day of the play’s first preview two weeks later — the men discussed their friendship, their collaboration and the play’s bumpy beginnings.

Here are edited excerpts from the conversations.

Q: Matthew, this is Kenny’s third play on the West End but it’s your debut. Does it feel like a milestone?

BRODERICK: I mean, I’m superstitious and I don’t want to, you know …

Q: Knock wood.

BRODERICK: Knock wood, exactly. [Looks around] There’s no wood. [Walks to a wooden table and knocks] When you’re a kid, there’s something very romantic about London. I’m embarrassed to say it, but it is sort of a dream to come here and do a play.

Q: Embarrassed?

BRODERICK: Well, it sounds hokey. And it also just sets you up for, “Be careful for what you dream for, you [expletive].” And wham, I’ll be smashed down to whack-a-mole. [Laughs] Don’t print any of that.

Q: Kenny, did you have Matthew in mind as Mark from the beginning?

LONERGAN: No. I started writing notes for it, or making attempts at scenes in it, when I was pretty early in my mid-20s. And the character could be anywhere from his early 40s to his early 50s — no older and no younger — so there’s no question of writing it for Matthew. But I believe that I thought at the time, “It’s too bad he’s not the right age because it’s a really good part for him.” He happens to understand what’s so beautiful about astronomy itself.

Q: What is that beauty?

LONERGAN: All you’ve got to do is go outside at night when you’re in the country and look up.

Q: Why the play’s long gestation?

LONERGAN: When I first wrote the play, I was a young man, not a 40-year-old man, and I really didn’t know what it was like to be in a relationship for 10 years, or to have the same job for 10 years.

Q: How much rewriting did you do?

LONERGAN: Almost none. I cut about 10 pages and I changed a few lines, a dozen maybe. And I changed half of those back. There’s always a tipping point where you start to feel that everything you’re doing is making it worse, not better.

Q: Matthew, you’ve also appeared in Kenny’s films, including “You Can Count on Me” and “Manchester by the Sea.” Who takes the lead when you collaborate?

BRODERICK: Gosh, that’s a good question. I always let Kenny be in charge — because I love him and I never don’t agree with him. And he wrote [“The Starry Messenger”], so my first job is to get him what he wants.

LONERGAN: [Laughs] I certainly have the final say over what he says in the play, and he has the final say over how he says it. But it’s really much more collaborative than that.

BRODERICK: Not to say we haven’t had a few screaming fights over nothing that don’t last. But no, we’ve never had a split in an endeavor, one of these plays or movies, never.

Q: What was it like putting on the original production amid all that negativity?

LONERGAN: There was a little tumult because I had never directed a play before. I was inexperienced and so our tech was not smooth. And we lost an actor late in the process. But I only found out that the play was supposed to be in trouble after I had read somewhere that it was supposedly in trouble.

Q: Matthew, what do you think Kenny is getting at in the play with Mark’s fixation on the unknowable?

BRODERICK: One of the arguments is whether there’s a God who has a plan, or is everything random? And why are we here? Is it possible to be here for no reason at all? And isn’t it better to admit that we absolutely have no idea about it even though that’s frightening?

Q: Where do you come down on that argument?

BRODERICK: I guess I’m more a science person. I don’t gravitate to a literal interpretation of the Bible certainly. My sister is an Episcopal minister, and she’s always saying: “You don’t get it. It’s faith, which you don’t have.” Do you want me to call her and get this worked out?

Q: Kenny, the Broadway revival of your play “The Waverly Gallery” recently earned two Tony nominations. Is “The Starry Messenger” headed there as well?

LONERGAN: I don’t think we’re up to that yet. But if it’s in the cards, that would be wonderful.

This article originally appeared in The New York Times.