Since the beginning of 2018, the Iranian government has locked up a number of environmental scientists and campaigners. One respected conservationist was found hanged in his cell in what the authorities said was a suicide. What is going on?

Stephen Sackur speaks to Kaveh Madani, a scientist invited back to Iran from an academic post in London to be deputy head of the environment department. He got caught up in the crackdown and fled Iran in April. Why has environmental activism become so dangerous in Iran? Show less