Are winds of change blowing across Iran? The Islamic Republic's new president, Hassan Rouhani, has engineered a diplomatic opening with the United States. There's optimistic talk of compromise on the nuclear stand-off and an end to Iran's international isolation. Where would that leave die-hard opponents of the regime? Stephen Sackur speaks to Reza Pahlavi, exiled eldest son of the late Shah of Iran and spokesman for the self-styled Iran National Council. Does a figure steeped in Iran's past have a role to play in its future?