Christmas may feel like it’s long gone now we’re steeped in the cold, dark days of January, but the company of Hull Truck Theatre’s The Flint Street Nativity is keeping the spirit of the season well and truly alive.

The adult cast brings Tim Firth’s comedic study of a junior school nativity play to life with enthusiasm and aplomb. Set in a classroom free of adult supervision, the children run wild during their preparations for the nativity, with fights over whose dolly should play Jesus, who is the best Mary and what stars are really made of. There’s real charm in the detail of designer James Cotterill’s brightly coloured schoolroom, which boasts plastic seats stained with spilt paint and glitter, a playhouse-come-stable, and an arts and craft area complete with childish drawings of the holy family featuring a “fat man” and a duck. Costumes, too, cleverly emphasise the characters’ youth, from a shepherd sporting oversized slippers to an angel embarrassed by the light-up wings her mum has made especially for her. From start to finish, this is a production that reminds us what the festive season is all about: the kids.

It has already been noted elsewhere that Firth’s tale of infant politics, first written for the screen, has been instilled with new life on the stage through the addition of carol singing. Or rather, attempts at carol singing. The children (with the notable exception of perfect student Jenny, portrayed immaculately by Elaine Glover, who determinedly mouths the correct words as the rest of the class descend into chaos) have not exactly learnt their words. This offers the opportunity for each actor to have their moment in the spotlight with solos revealing the children’s innermost thoughts. From Lauren Hood’s jealous and tortured Angel Gabriel to Laura Elsworthy’s side-splittingly straight-talking Shepherd, these children are far from shrinking violets, and song provides the perfect vehicle for both rowdy ramblings and crushing confessions.

Comedy is of course at the forefront and is more often than not generated by the children parrotting their parents. Whether it’s Elsworthy’s Shepherd using her farming experience to give no-nonsense advice on how babies are born (“You moo a lot”) or Lucy Beaumont’s starstruck Wise Man informing everyone that playing Bingo is how you “get things”, the laughs come thick and fast. There are priceless moments too numerous to count, and the skill of this flexible cast lies in the actors’ ability to create 10 completely individual characters, ranging from Frazer Hammill’s fantastically loveable geek to Al Nedjari’s lisping loner to Rina Mahoney’s Angel, desperate to be liked but tormented by the cruel games young girls play. Snapshots of adulthood are littered throughout the play as the children talk about their mums and dads, and much hilarity is provided by James Holmes’ Joseph, obsessed with Question of Sport, and Dale Meeks’ dedicated devotion to the unattainable Jenny.

There is something deeper too in these moments of adult impersonation. In one interlude set in the storeroom, Hood shines as she smears red lipstick round her mouth and imitates her mother, capturing the perfect balance of childish innocence and a painfully accurate observation of a mother. Moments like these build to the climax of the play, which sees the action shift from the nativity play to a parental gathering afterwards. The transformation is impressive as the cast agilely adopt the parental roles but maintain resonances of the relevant child. The tone subtly but surely shifts as more of the parents gather, and the comedy cuts closer to the bone. Firth gradually reveals the weakness, fear or paranoia of each parent, culminating in an achingly beautiful moment between Glover’s PTA super-mum and the wonderfully woeful Neil Caple. The confession that his son doesn’t know he’s separated from his wife is gently met with the heartbreaking truth: “He’s a seven year old boy. He’ll have known before you did.” Caple and Glover create a devastating moment genuinely stunning to behold that will surely stay with the audience for quite some time to come.

To say that The Flint Street Nativity far supersedes its comedic beginning is to in no way diminish its triumph. It is testament to it. An acute observation of parents and children alike, it is the laughter itself that ultimately reveals the pain lurking beneath the bravado. An exuberant and energetic cast get the balance just right and give voice to emotions so true to life that they will send you home with a smile on your face, an ache in your chest and a tear in your eye. Heartbreakingly hilarious.

The Flint Street Nativity plays at Hull Truck Theatre until Saturday 14 January. Tickets and more information available from Hull Truck Theatre’s website here.