Jeremy Corbyn claims that Labour now represents the political mainstream. Is that really true? Where does it leave the Tories? What can Theresa May do about it? We trawl the data to try to find the elusive centre ground of British politics. Plus we ask whether mainstream regional politicians like Ruth Davidson and Sadiq Khan can speak for the whole of the UK. If they can't, who on earth can? With Mike Kenny, Professor of Public Policy at Cambridge, and Helen Thompson. *recorded before Theresa May's speech*