Though clouds still loomed and the ground remained squelchy underfoot, Olivia Dean brought a welcome calm and undeniable warmth to BST Hyde Park’s Great Oak Stage on Sunday afternoon. Following a weather-disrupted opening set by Amber Mark — whose performance was cut short by a torrential downpour — Dean arrived as the skies cleared, bringing poise, polish, and powerful vocals to a crowd that refused to let a bit of British summer rain dampen their spirits.