Mr David Cameron has attacked British universities for failing to tackle extremism on their campuses.
In a speech setting out a five-year plan to counter extreme views, the British Prime Minister accused university leaders of "looking the other way" when Islamist extremists speak on campus. This, he said, was "through a mixture of misguided liberalism and cultural sensitivity".
For many people, this message is clear - Britain welcomes diverse opinions and viewpoints within certain "bounds of acceptability".
If you want to have a debate over the role of religion and civil society, that's perfectly acceptable, but host a speaker with beliefs in line with what the government considers an unacceptable version of Islamic thought and you are out of bounds.
Arguments against free speech absolutism often rely on examples where public opinion clearly opposes a speaker or group (such as Nazis or those espousing extremist views in the name of Islam), and this is what makes the bounds-of-acceptability arguments fronted by Mr Cameron so dangerous.
The right to free speech exists precisely to protect whatever speech the majority finds abhorrent and so is inclined to censor.
Many of the ideas that led to substantial moral progress in history emerged out of viewpoints that swam against the currents of public opinion.
And as John Stuart Mill famously noted, even odious ideas can lead to progress, as we sharpen our understanding of the truth by observing its "collision with error" in public debate.
The crucial problem with bounds-of-acceptability restrictions on free speech is that different sub-groups draw the lines differently.
The British public, writ large, may wish to curtail discussions of the more radical views espoused by a minority of those who identify as Muslim - but some students on university campuses have different expectations. They are more likely to demand the removal of credentialled ambassadors of the State of Israel, for example.
The disparity between what the British public wants and the demands made by students on university campuses (or any other sub-group for that matter) is not surprising because, in the absence of a constitutional backdrop giving firm legal standing to free speech - such as exists in the United States - people will become highly situational in their preferences.
Mr Cameron and the Home Secretary, Ms Theresa May, are trying to define the boundaries of free speech in Britain. They are not the first to do so, but they are taking the country down a decidedly illiberal road.
If bounds of acceptability can be moved so easily, different sub-groups will start making demands that free speech protections be narrowed. And as we have seen, different groups deem speakers and ideas of different stripes as unacceptable, so the circle of permissible debate in Britain may close very rapidly.
As long as we permit majorities to curtail speech they dislike, be they majorities in Westminster, or student governments or management teams on university campuses , liberty will remain insecure. Only the legal entrenchment of a capacious right to free speech would avoid these shifting sands and guarantee genuine free speech for all.
•The writer is Professor of Government at University of Essex.
A longer version of this article first appeared in theconversation.com, a website that carries analysis by academics and researchers in Australia and Britain.