Bono flew to Barcelona on Saturday at the invitation of Naomi Campbell, to take part in Frock 'n' Roll, a fashion and music industry tribute to Nelson Mandela.
Novelist Salman Rushdie was in hiding for fear of his life for many years. Then he showed up onstage with U2. Then he wrote a song with them. In this extract from a piece in The Sunday Times he recalls how it all came about.