Over the last two weeks we have reported on a series of secret talks between the US and Iran over the Islamic Republic's nuclear programme. Contacts in Turkey between Washington's and Tehran's representatives were taken a step farther in early October when the Supreme Leader's top aide on foreign policy, former Foreign Minister Ali Akbar Velayati, met unnamed US envoys.
So how significant are these "back-channel" talks in a possible path to diplomatic settlement, rather than war? We explain in five minutes: