There are things that get said only for the shock factor, and then there are things that are just shocking. Plan B's subject matter, with its colourful landscape of drug dealing, stabbings and genital warts, doesn't make for cosy chats around the breakfast table. The rapper's manner is equally high-impact, as he snarls at the mic like an alsatian that has just broken free from its muzzle. Yet the 21-year-old east Londoner (real name Ben Drew) delivers his tirade with such idiosyncratic elegance, not to mention passion, that the ends entirely justify the means.

Women fare strangely well in his dark landscape: sisters who need protecting from abusive boyfriends, or the perils of underage pregnancies. Plan B's songs are morality tales in which a child tries to be a parent. "You're too old to be naive," he tells the mother character on Mama, begging her to see sense about her crackhead boyfriend. "It's not how the man of the house acts/ I got to defend my territory, guard my patch." (His own mum is in the audience tonight.) On the refrain of Kidz, he sounds positively old-fogeyish, tutting: "That's the mentality of kids today."

He also takes a swipe at a journalist who has labelled him a folk artist - yet the description is oddly apt, and not just because of Drew's populist concerns. A committed musician, he claims to be as influenced by Nirvana and Rage Against the Machine as by rap, and strums a guitar in a very deliberate, finger-picking style throughout the show. Tonight sees the debut of his new live band, and while the backing singers look like mates who have been drafted in to help, the cellist adds something gorgeous and poignant. whether he really needs all those people on stage with him is open to question.