Tony, one of several hundred dancers who are making the 100 Club dancefloor a sticky place, tells me he last saw the Beat 20 years ago. It probably coincided with their last top 10 hit, in 1983, after which the much-loved Birmingham ska stars went the same way as the rest of the politicised ska scene. But two decades on, Tony hasn't forgotten the "rude boy" dance, in which elbows play as big a part as feet. As what's left of the original Beat squawk into action with their 26-year-old debut single, Tears of a Clown, his arms whir like pistons and his body convulses. You'd call an ambulance if everyone else weren't shuddering in exactly the same way.

The Beat probably generate similar sweatiness whenever they semi-reunite for the sporadic club dates. Like Madness - another venerated fusion of Jamaican rhythms, white pop and Mod-inspired fashion - they are embedded in the teenage memories of the pre-rap generation, now pushing 40.

These days, the operation is headed by former sideman Ranking Roger, whose stage name, once the height of rudey coolness, now sounds as archaic as Toasting Terence or Singing Sidney. Aided by his comely son, Ranking Junior, he runs a tight ship: purveying booming lead vocals and overseeing the backing band's pin-sharp renditions of Too Nice to Talk To, Mirror in the Bathroom and the Clash's Rock the Casbah. "No computers or drum machines, none of that stuff," he notes proudly. Junior, perhaps realising the pointlessness of competing with Dad, simply wails his stock phrase: "Rude boys! Rude girls!"

Nostalgia act that they are, the Beat are worth catching, if only as proof that the UK top 10 once regularly accommodated a band that served up politics as both main course and dessert. Hard to believe, isn't it?