As Boyce Avenue frontman Alejandro Manzano tells us during a between-song pause, Boyce Avenue your usual pop-rock trio: they get no radio play or TV promotion, yet here they are, selling out the 2,000-seat Indigo. It's the 10th time the Floridians have played London – on a previous visit, they supported One Direction – and the venues keep getting bigger.

Their success is entirely due to having spent four years uploading videos of themselves covering chart hits, racking up tens of millions of views. They're the figureheads of the YouTube pop star phenomenon – unsigned acts who achieve decent-sized success with no mainstream industry involvement. The bewildering popularity of Boyce Avenue's covers – no better or worse than that bar-band down the road - has spurred them to self-release original material; tonight's set is weighted toward their own songs, suggesting they're aiming for a future where they stand alongside Avicii and Bruno Mars rather than covering them.

But in the pre-digital age, Manzano and his brothers Daniel (bass) and Fabian (guitar) probably wouldn't have got as far as London, let alone played their Maroon 5-ish pop to a crowd that booty-shakes as if it were Maroon 5 themselves rocking out in black-and-white uniforms. Their original songs are heartfelt but platitudinous, and Alejandro manifestly lacks the frontman mentality, a problem in a band trying to move to the next level, where personality is the decider.

To be fair, his high, sweet croon occasionally packs the kind of punch that made Mars and Usher household names – he invests Rihanna's We Found Love with a yearning that makes it the night's highlight - but Boyce Avenue's popularity seems to be linked to the idea that three good-looking men plus catchy covers will never go out of fashion.

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