Saturday. 9:30pm. I’m sitting cross-legged on the grass of Chapelfield Gardens, and all around me the Garden Party is still going strong. The Adnams Spiegeltent is a roar of chatter and noise, and beside it a large mechanical dragon — rather charmingly named Elsie — turns the air orange with the glow from her flamethrower-covered body. I’m not here for either of those events, great though they were. I’m here for Pedal-Powered Car Chase, a fifteen-minute performance involving inventive live music, a handful of plucky volunteers, and some exercise in the name of making us think.