The Assembled Parties review – Christmas comes early in a crackling family comedy

Bing Crosby is singing, a goose is resting, and a noisy aunt is commenting on everyone’s weight: it’s enough to make you double-check your calendar. This may be October, but there’s already a giant Christmas tree in the middle of the Hampstead theatre stage, which James Cotterill’s stylish design has transformed into the Upper West Side apartment of a non-religious Jewish family gathering for the holidays.

Christmas may come earlier every year, but it has taken a while for this one to arrive: this is the UK premiere of Richard Greenberg’s Broadway hit from 12 years ago. It’s 1980, and the “ruthlessly” cheerful Julie is hosting along with her husband Ben, whose hopes for his college-age son Scotty extend all the way to the Presidency. Scotty’s earnest Harvard friend Jeff navigates his way naively around both the apparently endless rooms and the extended clan, which includes an “odd” cousin and a sketchy brother-in-law.

Daniel Abelson as Ben and David Kennedy as Mort in The Assembled Parties at Hampstead theatre. Photograph: Helen Murray

And then there’s Tracy-Ann Oberman as Ben’s sister Faye, in a performance so enjoyable that even facing upstage, the back of her glamorously coiffed head beams out charisma. “I love what you’re wearing,” she tells Julie. “Is it your mother’s?” Blanche McIntyre’s direction keeps the finely tuned comic dialogue rattling along in the first half, even as nothing happens and we wonder, along with the characters, exactly what story we’re in, “I’m just a character in a farce,” says Julie; “we’re in a potboiler here!” announces Ben.

Really, we’re in the kind of old-fashioned play that Jeff’s mother has always loved, with impossibly “breezy dialogue” and charm. Only when we return after the interval – to the same family apartment, 20 years on – does the dramatic narrative reveal its shape, as Greenberg underscores familial patterns – such as Faye’s relationship with her daughter, and her own mother – with the cyclical nature of political change.

Fine acting allows a crackling script to develop true warmth and Alexander Marks doubles brilliantly as the easygoing Scotty and his nervous, feckless younger brother. Sam Marks yearns sweetly for intimacy as Jeff, both the young man silently smoothing his friend’s pillow and the confident lawyer still a little in love with his friend’s mother, while Jennifer Westfeldt’s Julie delivers the second-act moments of heartbreaking tenderness. It’s a Christmas well worth waiting for.