Frank Turner's success goes to show that Eton produces more than just pillars of the establishment. This particular Old Etonian, a former classmate of Prince William, has acquired a fervent following by dint of an uncompromising attitude toward authority. Of the 18 songs played here, at least half stuck two fingers up – loudly, and with much swearing – at what he perceives to be the bad guys: government, big business and "anyone who tells you how to live".

Turner's folky rock is informed by Billy Bragg and the Levellers, though the audience at this sold-out show looked almost too young to have heard of either. Turner, then, is their generation's entry-level protest singer, and it wasn't hard to appreciate why he had such a galvanising effect on this crowd. After all, what's not to like about a good-looking 27-year-old singing passionately about righteousness?

Whether delivering an a cappella version of folk staple Barbara Allen or introducing his own song Sons of Liberty with a lecture about the Peasants' Revolt ("Wat Tyler told the king and his ministers to fuck off"), Turner's air of being here to set the world to rights never wavered. His reward was an audience who sang along lustily, not just to tracks from the current (third) album, Poetry of the Deed, but to Smiling at Strangers On Trains, a relic from his stint with London punks Million Dead.

Turner is capable and engaging, but not especially original or nuanced. His tunes divide the world into Us and Them (ie politicians and fat cats); his advice to Them is simply, as in Sons of Liberty, "Go fuck yourself." He can, and hopefully will, do better.