A woman stands on a rooftop listening to the sounds of the city below. There is only the dull hum of traffic tonight. But she knows how easily that can change. It is usually the dogs who notice the sound first and begin to bark furiously. The noise of aircraft. Then the ominous percussion of explosions. A ball of orange rising from an airstrike in a familiar neighbourhood. The BBC has obtained footage and interviews from Tehran which evoke a city of strained nerves, of constant waiting for the next blast and relentless fear of the state security apparatus. Baran – not her real name – is a businesswoman in her thirties. She is now too scared to go to work. "With the start of the drone attacks, no one dares to go outside. If I open my door and step out, it is like gambling with my life." She lives alone but is in constant communication with her friends. "My friends and I message each other constantly asking where everyone is…and even when there is no sound the silence itself is terrifying.…