Ed Sheeran has had a huge year. He joined the Rolling Stones onstage, partied with Keith Richards, sold out three nights at London's Wembley stadium and, this past weekend, turned up at the Global Citizen Festival in Central Park, where he duetted with none other than Beyoncé and Coldplay's Chris Martin. We shadowed the 24-year-old British star for the full day, catching both private moments and onstage triumphs.