It was June 6, 1989. Not hundreds of thousands but millions of people poured onto the streets of Tehran to bid farewell to Ayatollah Ruhollah Khomeini, the leader of Iran’s Islamic Revolution. The sheer scale of the mourning crowds completely overwhelmed security arrangements. At least eight people were killed in stampedes, and around 11,000 were injured.The funeral procession was later recognised by Guinness World Records as the largest funeral gathering in history. At the time, an estimat...