Ayatollah Ali Khamenei has been killed on the first day of massive US and Israeli air strikes on Iran, US President Donald Trump has announced. The death of the 86-year-old ruler of the past three decades - one of the longest in the world - was later confirmed on Iranian state TV. Iran has had only two supreme leaders since the 1979 Islamic Revolution. It's an all-powerful office - the supreme leader is head of state and commander-in-chief of the armed forces, including the elite Revolutionary Guards. Khamenei is not quite a dictator, positioned in the middle of a complex web of competing power centres, able to veto any matter of public policy and hand pick candidates for public office. Young Iranians have never experienced life without him in charge. State television has covered Khamenei's every move. His image is plastered on billboards in public spaces and his photograph is ubiquitous in shops. Abroad, successive Iranian presidents have often hogged the limelight.…