Imagine you are running a mid-sized university, and you get a call from the Chinese embassy expressing concern that one of your professors has an annoying habit of speaking out against the Communist Party. A senior politician is visiting your country next week, says the caller. It would be embarrassing if your professor made any media appearances during that time. There would be consequences.

This is ridiculous, you think. But you are rather reliant on fee income from Chinese students. So you send a message to the professor concerned. You ask him, as a personal favour, to refrain from publishing or speaking that week. Nothing is written down, nothing has changed. Except one thing. You have crossed the Rubicon. You have sacrificed academic freedom for money. And that can become a nasty little habit.