The BBC Proms is the world’s largest classical music festival, and the unique spirit that permeates the concerts comes largely from the Prommers, a diehard group of music fans who show up early for every concert and take their place in a huge, standing-room-only pit in front of the stage. “It’s hardly surprising that, over the years, the tastes and foibles of the Promenaders have been projected on to Proms audiences as a whole.”