Balthazar have been buzzing around Spotify’s indie playlists for a few years now – their debut album Applause was released back in 2011. But this sell out Scala show, an obligatory rite of passage for bands looking to take their standing to the next level, is their biggest to date in London, and a huge step for them ahead of festival season.

The audience is mainly continental – snippets of French, German and Dutch ricochet off the venue’s narrow corridors – and range from teenaged to middle-aged. It’s worth noting that Balthazar are chart-topping stars, rather than indie newcomers, in France and their native Belgium.

Support comes from Faces on TV, a one-man band who produced Balthazar’s latest album Fever. His songs combined earth-shattering bass, eerie Thom Yorke-style vocals, and various other looped elements including drum pad, guitar and flute. It was a spectacle to watch him create these indie oddities, but the end product lacked cohesion.

It’s customary for the main auditorium to empty between the support and the main act, as patrons flock to the bars. Maybe it’s because it’s a Tuesday, or maybe because the crowd is so intent on keeping a clear view of the stage, but most punters stay rooted to the ground throughout, to the point where you wonder where they’ve cultivated such resilient bladders.

As Balthazar take the stage under ominous red lighting, it quickly becomes clear that their setup borders on the idiosyncratic. Lead vocals are shared between two guitarists Maarten Devoldere and Jinte Deprez, though they both switch between a lazy baritone drawl and piercing higher registers, so it’s often hard to tell who is singing which part.

On the right-hand side wearing high-tops is the band’s violinist, trombonist and occasional extra guitarist – known only as Dave. Completing the ensemble are the bassist and drummer whose tight command of the rhythm section proves especially crucial in the band’s new material, much of which verges into the territory of Jungle’s bassy fusion of soul and house music.

This said, it is immediately clear that Balthazar’s roots are in guitar music. ‘The Boat Man’ is an early highlight, with its funky groove eventually building up to a crescendo of shredding under flashing lights. It feels like a show climax, and we’re only two songs in. ‘Sinking Ship’, with its lazy vocals and addictive riff, feels like a leftover Blur tune, while new tracks like ‘Wrong Vibration’ and ‘Wrong Faces’ hit the spot with the audience, the latter of which features a swirling violin breakdown in the manner of Britney Spear’s ‘Toxic’.

The band arguably stuff too many new songs into the set’s middle section – things drift slightly, and the crowd grow restless, until the menacing piano chords of ‘Decency’ bring things back to more familiar territory. The slow-building guitar anthem ‘Blood Like Wine’ leads to one of the night’s few singalong moments, as does ‘I’m Never Gonna Let You Down Again’, a recent single and their strongest to date, with an irresistible chorus that almost channels the Scissor Sisters in their heyday.

Despite some intermittent technical issues which plague both acts, there seems to be something warm and intangible binding this European crowd together at Scala, over and above an accomplished and mutedly entertaining show from Balthazar. Whatever it is, lord knows we could use more of it in the UK right now.