“Purple emperor-watching with Matthew and Neil is not your average butterfly entertainment, ethereal and somewhat effete. Theirs is a raucous, adrenaline-fuelled spectator sport. The emperors themselves seem to play to the crowd. Pugnacious males dart around the crowns of oaks, staking out their territory, jetting about with muscular flicks of their wings, twirling on their own axes, elevating a hundred feet into the air. They are the SAS of butterflies, fit, fearless and chemically armed.”