Lonergan wows crix with double-header

Six weeks ago, London barely knew his name. Now, Kenneth Lonergan is the London theater’s American discovery du jour on the basis of two well-received openings within one month.

“He’s king of the West End,” says Clare Lawrence, co-producer of “This Is Our Youth,” the 1996 Off Broadway play (revived in New York in 1998) that had its British preem March 15 at the Garrick Theater.

Whereas the New York run gave an early showcase to a young actor, Mark Ruffalo, who has gone on to be a film name (not least in writer-director Lonergan’s own “You Can Count on Me”), the London “Youth” looks set to be a temporary resting place for visiting Hollywood stars.

The initial, and hugely accomplished, trio of Jake Gyllenhaal, Hayden Christensen and Anna Paquin finished their limited stand April 20, with the somewhat older (and, arguably, starrier) trio of Matt Damon, Casey Affleck and Summer Phoenix stepping in for eight weeks starting April 22.

Further replacements are possible, either via a summer transfer to another theater — the Garrick has Martin McDonagh’s Royal Shakespeare Co.-spawned “The Lieutenant of Inishmore” booked to follow “Youth” in mid-June — or in the autumn, in which case Jeremy Herbert’s set would be put in storage.

Is this, then, the young-celeb version of “Art,” the Yasmina Reza long-runner currently climbing its way toward a 30th London cast?

“I have heard it called that,” acknowledges Lawrence, a 26-year-old Cambridge grad who, with colleague Anna Waterhouse, has been working for some 10 months with Lonergan’s New York agent, George Lane, on bringing “Youth” to Britain.

“As a play,” she goes on, “Youth” “sort of lends itself in the same way to longevity. It’s similarly character-based rather than plot-driven, and each new cast reinvents it as a new piece.” And as with “Art,” she says, “it’s more to do with a combination of people than individual actors; they have to really be able to work together.”

That shouldn’t be hard with the incoming trio of Manhattanites: Damon and Affleck are longtime chums — Damon won his screenwriting Oscar for “Good Will Hunting” alongside Casey’s elder brother, Ben — while Affleck and Phoenix are, as they say, an item.

Originally budgeted at £300,000 ($430,000), Laurence Boswell’s production will spend another $145,000 or so putting in the new cast with an assist from company director Rebecca Gatward and Lonergan himself. (Boswell is doing double duty at the moment, helming Madonna’s imminent London legit bow in “Up for Grabs.”)

With a 60% breakeven in the smallish Garrick (the 680-seater has been slightly slimmed down to accommodate the set), Lawrence hopes to recoup by the second cast’s June 15 end date — with Damon’s West End debut a box office bonus the play hasn’t so far had.

If hip casts are “Youth’s” catnip, it’s Lonergan’s subsequent “Lobby Hero” that really landed with local crix following an April 10 Donmar debut as part of that theater’s seasonlong series of five American work.

The Guardian’s Michael Billington called “Lobby Hero” “an even better play than the same author’s ‘This Is Our Youth,’ ” adding, “On the London evidence, Lonergan looks like one of American theater’s brightest prospects.”

The Times’ Benedict Nightingale wrote, “I’d rate ‘Lobby Hero’ above his ‘This Is Our Youth,’ ” going on to praise “a play to relish, a young American author to watch.”

Contrast these notices with the astonishingly sour Los Angeles Times pan of the same play (at South Coast Rep) in late February, which concluded, “The whole thing would be somnolent, if it weren’t so irritating.” Nevertheless, Lonergan is colonizing SoCal much in the same way he’s arriving in force in London: In addition to “Lobby Hero,” Southern California saw two productions of “The Waverly Gallery” this spring.

Speaking prior to its London bow, Donmar a.d. Sam Mendes said “Lobby Hero” and Lonergan were essential newcomers to the capital: “Kenny’s astonishingly unproduced here — astonishing, given that his writing is so beautiful.” And while “Youth” finds a British director steering North American actors through the play (OK, Paquin is from New Zealand but lives in New York), “Lobby Hero” offers the reverse: American director Mark Brokaw working with a quartet of Britons.

Mendes says Brokaw’s presence was essential to the Donmar venture: “I wanted (the play’s) American-ness to be retained.” “Lobby Hero,” too, looks likely to have a longer life, with discussions afoot for a commercial transfer starting mid-June.

How is the author taking the newfound attention from Blighty? “I’m just thrilled; it’s like a dream come true,” he said, speaking 48 hours before he, wife J. Smith-Cameron and baby daughter Nellie were due to fly home to New York.

On one hand, he expressed some bemusement at the British critical embrace of “Lobby” at the slight expense of “Youth” as might be expected from a culture where the issue-led play will almost always win out: “I feel it may be easier for English critics to pigeonhole ‘This Is Our Youth’ as a naturalistic examination of teenagers without that much more to say and to like ‘Lobby Hero’ because it has a large focus on public issues and the criminal justice system.”

On the other hand, he said, “Obviously you’re happy when anyone says anything nice about you.”

“I’m happy with the productions; I’m happy with the response. What do I have to be unhappy about?”

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