Soon after his private jet touched down on August 24th at Le Bourget airport, on the outskirts of Paris, Pavel Durov was arrested by French police. A statement later released by prosecutors said that the 39-year-old billionaire had been detained as part of an investigation into Telegram, the social-media app of which he is the founder and chief executive. French judges have until August 28th to decide whether to pursue charges or release him.