Professor Biggar:

You are right that, by its nature, it is hard to detect and measure, but there is plenty of anecdotal evidence, and I can tell you from my own experience. The clearest evidence of fear and self-censorship among academics was mentioned by Arif Ahmed earlier: his experience in Cambridge of spending a month trying to get 24 academics to put their heads above the parapet to sign a bit of a paper backing a motion against university policy. It took him a month to get 24 people to do that, but when the vote was held by secret ballot, it went overwhelmingly against the university, by several hundred academics. When those academics were liberated to express their views in secret, they did it, but they would not do it in public. That is one instance, but I think it is a signal instance. I urge you not to underestimate the degree of fear, even among senior academics.