The Roc was in the building at BBC Radio 1 Hackney Weekend 2012. After wrapping the “Watch the Throne” tour the prior night, Jay-Z returned to the stage, headlining Day 1 of the festival in London. The hip-hop mogul surprised concertgoers by bringing out Kanye West, M.I.A., and Rihanna. The pop princess, who will headline Sunday’s festival, performed “Run This Town” with her mentor as Beyoncé, Rita Ora, and Solange looked on.