LONDON — By conventional measures, dart players are not the telegenic type. They mutter to themselves onstage. They wear flamboyant polyester polos. They cradle their handful of tiny spears and stare a lot at a fibrous board seven-feet, nine-and-a-quarter inches away.

But professional darts has catapulted itself from musty British pubs onto millions of television sets across Europe, an insurgency by a working-class sport that has turned the best of its mostly middle-aged players into stars.

The premier darting event, the William Hill World Championship, has grown into a three-week, $3-million-purse affair, replete with cheerleaders and thunderous walk-on music, and the sport’s promoters work tirelessly to ratchet up the show.