The infamous Chinese spy balloon that was spotted and shot down over the US earlier this month is now being picked apart at an FBI lab. What we don't know yet is what exactly were they doing over North America? The balloon loitered over Montana and was looking down at a site where the US houses nuclear intercontinental ballistic missiles. To talk about the broader spying relationship between Washington and Beijing, I'm joined by FT's US China correspondent Dimitri Sevastopulo.