As proof that good things come in packages that are not just small but sweet and sorrowful, along comes the European premiere of Jonathan Larson's "Tick, Tick ... BOOM!" to further detonate an already revved-up London musical landscape. Revisiting the show with an entirely new physical production and cast dominated by a smashing turn from Neil Patrick Harris as the authorial alter ego, its Off Broadway helmer Scott Schwartz has once again done an ace job of keeping airborne a piece that could slide into self-pity.

As proof that good things come in packages that are not just small but sweet and sorrowful, along comes the European premiere of Jonathan Larson’s “Tick, Tick … BOOM!” to further detonate an already revved-up London musical landscape. Revisiting the show with an entirely new physical production and cast dominated by a smashing turn from Neil Patrick Harris as the authorial alter ego, its Off Broadway helmer Scott Schwartz has once again done an ace job of keeping airborne a piece that could slide into self-pity. Moment by moment, “Tick, Tick” is the most emotionally satisfying musical London has seen so far this year.

This musical’s success was by no means a foregone conclusion in Blighty, and even as it is, one hopes its ceaseless yearning and exuberance don’t fall foul of the same hardened London hearts that were quick to dismiss “Rent” this side of the pond. Put together posthumously with Tony winner David Auburn (“Proof”) on hand as script consultant, this production further solidifies the sense of the seismic injustice of Larson’s early death — even as the show’s book affirms a life of action that, the lyrics to the final song tell us, “speaks louder than words.”

Larson’s empathy for his characters speaks loudest of all in this tale of a struggling Broadway composer, appropriately called Jonathan (Harris), who wants to write “the ‘Hair‘ of the ’90s” and just may have Stephen Sondheim on his side as mentor. On the other hand, why should Jonathan aspire to a Broadway where “every show’s from London” and tickets cost $50? (There’s a period piece for you.)

When not angsting about the workshop of his long-aborning musical “Superbia,” Jonathan must juggle the slow fade from his life of one g.f., dancer Susan, and the arrival of another (Cassidy Janson winningly assumes both roles) with the absorption into corporate America of best friend Michael (Tee Jaye), who delivers his own revelation by show’s end. Worst of all, Jonathan is turning 30.

One can imagine the exact same material turning in on itself: Why should we care about three clearly attractive, creative people whose problems are far from unique? But that’s to discount the rush of feeling in Larson’s score, which can pastiche Sondheim (“Sunday”) as deftly as it sets the pulse racing on show opener “30/90″ and the duet that follows, “Green Green Dress.” (Only “Come to Your Senses,” the one song we actually hear from “Superbia,” falls short of the mark, coming off as closer to the very “Les Miz”-style anthemic anonymity Jonathan derides.)

And it’s certainly to discount a terrific Anglo-American cast, who deliver “Tick, Tick” even more sharply than was possible Off Broadway, where the venue was almost twice the size of the musical’s London home. Both Janson and Jaye have fun with the other parts they are briefly asked to assume, from Jonathan’s relatives to a squawking-voiced agent who suddenly reasserts herself at his time of need.

Waspier in appearance than the part’s originator, Raul Esparza, Harris is simply remarkable in his London debut, striking up an easy rapport with the audience that leaves one hanging on Jonathan’s every tussle — and triumph. (His interplay with various aud members is just right, too: appropriate to the circumstances but never arch.) On the same sure-footed vocal ground heard last year on Broadway in “Assassins,” the performer makes something both charming and eloquent out of self-doubt and indecision.

He’s funny, anxious and agile (the choreography is by Christopher Gattelli, of “Altar Boyz”) in equal measure, and as the tick-ticks mount, Harris leaves us sharing in the tension surrounding Jonathan’s success.

Is he Jonathan Larson? Not literally, since the show must work as fiction, not autobiography. But as the cast blow out the candles near the show’s climax, one is left feting the exhilaration of a small-scale musical jewel while mourning the loss that underlies the score’s every hard-won note.

Tick, Tick. . .Boom!

Menier Chocolate Factory, London; 155 Seats; £20 ($32) Top

Production

A David Babani and Danielle Tarento presentation of a musical in one act with book, music and lyrics by Jonathan Larson. Directed by Scott Schwartz. Musical director, Caroline Humphris. Choreography, Christopher Gattelli. Script consultant, David Auburn.

Creative

Sets and costumes, David Farley; lighting, Colin Grenfell; sound, Gareth Owen. Opened June 10, 2005. Reviewed June 12. Running time: 1 HOUR, 40 MIN.

Cast

Jonathan - Neil Patrick Harris Michael - Tee Jaye Susan - Cassidy Janson
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