My first days as a Brit at Harvard coincided with the horrors of 9/11. In need of comfort and unable to tear ourselves away from the news, teenagers of all nationalities squashed on to sticky seats and watched the towers fall again and again on the common room TV. All shocked. All together. That moment, and the days that followed, taught me more about the strength of a community outside my own than anything since.

No longer. Last week, in the latest escalation of the US president’s fight against Harvard, the Trump administration banned the university from enrolling international students “effective immediately”. The reason? Harvard’s alleged failure to act against antisemitism and the teaching of “woke” ideology. “Let this serve as a warning to all universities and academic institutions across the country,” read the ominous statement from Kristi Noem, the secretary of homeland security.

A warning to do what? Bend the knee to the president obviously. (Harvard hasn’t and the ban has been temporarily blocked in the courts.) But Trump’s move also holds a larger unintended warning about ideas, academic freedom and America’s involvement with the rest of the world.