Slow Club, Union Chapel, London

“One day we’ll be a bloody serious band, Charles,” Rebecca Taylor (mostly) jokingly chides her doubting co-Slow Clubber Charles Watson, as a song’s start collapses in a heap.

“You and me need to believe we’ll be the Kings of bloody Leon.” Packed into pews in this beautiful north London church, we can only pray such an awful fate never occurs. Though this Sheffield duo (plus live bandmates) briefly orbited the pseudo-folk world of Mumford & Sons, Noah and the Whale and Laura Marling, this isn’t a club built for mass membership. Two albums in with this year’s Paradise, Taylor’s ambition is genuine. But their music’s sweet spirit, sharpened by heartfelt observation of hurt, needs intimacy.

They begin this Christmas show with an a capella take on Pulp’s “Disco 2000”, turning their fellow Sheffield band’s old hit into a nostalgic carol. “Only If You’re Certain” then lets Taylor strum and sing the complaint of a rejected lover refusing to let go, her red lips in a pained pout. You can hear a door creak, and if a pin had dropped, maybe that too. The woolly-hatted, gentle Watson has a cool, clear voice, prettily expressing longing. When they combine for “Everything is New”, Taylor offers him bratty vocal support. Anything daft or extreme, from rambling jokes to yelps of pain, is her job. Her mum sits next to me, happily cackling.

“Hackney Marsh” imagines east London’s wilderness as a landscape allowing personal reinvention, to be rowed on “a raft of new beginnings”. The foot-stomp heart-rhythm of “You, Earth and Ash” pictures a more stunned emotional scene, resolved by Taylor’s defiant howl. “You are the only one, the only one that counts,” they sing on “Gold Mountain”, a grasp at a sinking friend which deepens in intensity as the plea quietens. The heavy rockabilly rumble of “Where I’m Walking” and fast Buddy Holly jangle of “Giving Up On Love” show that even when rocking out, their inspirations are thrift-shop sweet. This is polite music by well-raised people wishing others the best, but knowing they won’t always get it.

They finish with their own Christmas songs, the pick of which is “It’s Christmas and You’re Boring Me”, where Taylor bluntly decides, “I’ve loved you as much as I can”. Clear truths, delivered with craft and conviction: Kings of Leon must dream of such class.