Tonight, as she has every night since Iran's disputed election, Leyla will walk up to the rooftop of her apartment building in Tehran and join the collective shouts of "Allahu Akbar" ("God is great").

The 10pm chorus - consciously borrowed from the protesters who prepared the way for the 1979 Islamic revolution - has become the rallying call of the protests seen in Iran over the past two weeks. It has the benefit of being anonymous, and allows people to express their anger without directly facing the threat of physical violence from the security forces.