Some things never change? Tehran students burn pictures of US President Barack Obama during a gathering this month to mark the 29th anniversary of frozen ties

President Barack Obama has his eye on Iran. For three decades Washington and Tehran have tormented each other. For two years Mr Obama has built his political identity on the idea of engaging with US enemies, with Iran as his most controversial prospective interlocutor. And for months, Israel has been warning Washington that its patience for watching Tehran’s nuclear programme gain pace is running out.