The power of the columnist

As Boris Johnson swaps his newspaper column for Downing Street, how much power do columnists really have? We convene a master class with three big name press pundits - Matthew Parris of The Times and Radio 4, Janet Street-Porter of The Independent and I-paper, and Sarah Vine of The Daily Mail.Also, what lessons can the media learn from the collapsed VIP sex abuse case, now that the alleged victim Carl Beech has been convicted of multiple counts of perverting the course of justice and fraud? Have efforts to reform police contact with journalists undermined transparency?Presenter: Amol Rajan Producer: Paul Waters