Labour’s electoral dominance in Caerphilly, deep in the party’s Welsh heartlands, has collapsed while Reform UK and Plaid Cymru have hoovered up votes. On a visit to the south Rhymney Valley ahead of a historic byelection, John Harris finds a polarised community, reminiscent of the final days of the European referendum contest. Kiran Stacey joins him to discuss the significance of the Caerphilly byelection, how it is being fought on the ground and online, and what it tells us about the future of UK politics. Plus, we look at problems facing the grooming gangs inquiry as a fourth survivor quits and the prime minister brings in the trusted trouble-shooter Louise Casey to try to shore up the process. And finally, Labour’s deputy leadership contest comes to a close … at last • Send your thoughts and questions to [email protected]. Help support our independent journalism at theguardian.com/politicspod