They’re back. London’s Proms concerts are the summer music fest every critic seems to love to hate. Big, showy, popular and rippling with gaudy nationalism, they also seem to grow each year. “As though to reinforce its paramountcy, the BBC has announced a season, to open on Friday, with more concerts than ever, more special events and an expansion of the Proms in the Park to embrace all four UK nations for the first time.”