It is extraordinary enough to see the world's top central banker make an unscheduled video statement on social media. My first thought upon seeing the post from the Federal Reserve chair Jerome Powell was: Is this an AI deepfake? That sense did not go away as I listened to what were indeed the real words of the world's most important financial official. The background here is a long-running spat between President Trump and the man responsible for setting interest rates in the US and indirectly much of the rest of the world. In theory, this has officially been about the cost of a renovation project at the Federal Reserve, the US equivalent of the Bank of England.