Love, loss and musical integrity fuel this endearing comedic fable, written by and starring Tom Basden and Tim Key, who transform their BAFTA-nominated 2007 short into a slim yet satisfying feature. TV director James Griffiths (Bad Sisters), whose only film credit to date is the underwhelming Cuban Fury, helms with freewheeling, appropriately folksy charm.

Key plays Charles Heath, a two-time lottery winner living an isolated life on the titular island who books Basden’s rock star sell-out, Herb McGwyer, for a private gig for half a million quid, putting him up in his ramshackle home. Unbeknownst to his bemused and bad-tempered guest, Charles has also invited along Herb’s ex and former folk-duo partner Nell (Carey Mulligan), who arrives with her American husband, Michael (Akemnji Ndifornyen), in tow. Fleabag’s Sian Clifford plays local shopkeeper Amanda, who is tickled by the visitors’ unusual requests.

Powered by Charles’ love of a pun, the script is witty and wonderfully daft, and the casting spot on. Basden and Key share a seasoned comic rapport, while a delightfully confused Clifford steals every scene she’s in. Mulligan, too, is charm personified, lighting up the screen when she arrives and seemingly enjoying herself immensely, even if her character is held at a slightly frustrating remove. Ndifornyen, unfortunately, feels wasted.

What’s most impressive is how well The Ballad Of Wallis Island works in some of its more serious themes. Herb’s journey back to his musical happy place might be a predictable one, yet it’s convincingly conveyed by an understated Basden. And through Key’s comedically masterful and emotionally nuanced turn, we see how Charles’ eccentricity and gag-making are his defence against loneliness and grief. Bit by bit, the quirkiness makes way for something more in a beautiful exploration of what music means to us.

The Ballad Of Wallis Island is in cinemas now.