At the stroke of midnight on Monday, for the first time in 17 months, the staff of the Piano Works nightclub pushed back the tables, cranked up the volume and threw open the dance floor to mark “Freedom Day,” a go-for-it gambit by Prime Minister Boris Johnson to end almost all legal requirements to maintain coronavirus social distancing measures in England. “You could just feel it. The pent-up demand. It was like a jack-in-a-box. It just went pop! And everyone went berserk,” Tristan Moffat, operations director of the club, told The Washington Post.