On her current tour, Charlotte Church has been denouncing "the mainstream", as if she hadn't spent her entire career in it. Biting the hand that feeds you is a risky strategy for a performer, still more so one like Church, whose CV includes a Loaded magazine award for funniest TV personality. Evidently, it's a chance she's willing to take, but will fans accept her transition from poperatic family entertainer to emo-rocker?

At this tiny gig, a handful voted with their feet, walking out halfway through. But it's unlikely they were noticed by Church, who was pouring herself into the music. It would be easy to be snide about her off-the-peg reinvention; if there was always a Welsh amalgam of Kate Bush, Bat for Lashes and Evanescence lurking within her, she suppressed it until now. But as she introduced a dozen new songs, it became clear that the switch from arias to emotional rock isn't such a stretch after all.

Central to both is her voice, which functions as a kind of nuclear deterrent – we were fully aware that if she unleashed its full power, the venue would crumble into a heap of bricks. Instead, there were tantalisingly coiled-up sighs and ululations, occasionally augmented by vocal loops that entwined eerily with her band's Killersish guitar rock.

Some of the songs were written after she gave evidence at the Leveson inquiry last year, and she positively bristled as she sang them. Mr the News, inspired by Rupert Murdoch, slammed together Vaccines-style pop-punk and a spoken rant that culminated in "Something tells me you hit the bottom!" Take that, tabloid proprietors! Then she dropped to her knees on Judge from Afar, which was full of Björkish loops and abstractions. None of it felt forced, and that was her trump card; whatever happens with this reinvention, Church is following her heart.

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