Last week, the Princess of Wales announced that she is undergoing treatment for cancer. It was preceded by weeks of speculation about her whereabouts that went well into conspiracy territory. How exactly did conspiracy theories move from the fringes to the mainstream? And what are the responsibilities of the "mainstream media" when covering them? Also on the programme, BBC Radio 5 Live celebrates its 30th anniversary and what Tim Davie's speech means for the future of the BBC.Guests: Chris Curtis, editor in chief, Broadcast; Nicky Campbell, presenter, BBC Radio 5 Live; Rachel Cunliffe, associate political editor, New Statesman; Dr Annie Kelly, journalist and postdoctoral researcher specialising in conspiracy theories.Presenter: Ros Atkins Producer: Dan Hardoon