Axel Rudakubana, who killed three girls in a stabbing spree at a dance class, was obsessed with violence but had no known ideology. His case has led to calls for a rethink of counterterror strategy.

Children perched on shoulders with a birds-eye view are wrapped in scarves and multi-colored hats. The spectators are a cornucopia of wool, Gore Tex, t-shirts and classic floor-length fur coats, ...