But with the other diminution of freedom of speech this past month we pass from the first of Mill’s defences to the second: the risk that an opinion being silenced might lead to the enfeeblement of truth.

In early October, an Australian “historian” called Frederick Toben was arrested as he passed through Heathrow. Held in custody under the European Arrest Warrant, he currently faces extradition to Germany for posting information on the internet of an “anti-Semitic or revisionist nature” which, while not illegal in Britain, constitutes a crime in Germany.

It is not currently hard to find people willing to condemn Holocaust denial or its near cousin, Holocaust diminishment. Nor, for now, is it hard to find experts who can refute Toben’s claims. But the question that the Toben case raises is whether, as the last survivors of the Holocaust die out, we want to risk a situation arising in which our most eloquent answer to Holocaust denial is a legal silencing. Deniers should be defeated in the open. For that to happen, the full range of opinions, including false ones, has to be available to us and succeeding generations, even when we are forced to hold our noses.

Sherry Jones has the right to mention Muhammad’s child-bride because it is a fact, borne out by the most distinguished Islamic scholars. Frederick Toben has the right to diminish the Holocaust because he forces us to know more and be better (not to get too Rumsfeld-ian) at knowing why we know what we know. Airing a truth is not the same thing as concocting a lie; but neither must be made impossible.

More books, not fewer, are needed. As John Milton famously put it, “As good almost kill a man as kill a good book.” Recent events suggest that there are people who would like to do both. They could have done with considering Milton’s follow-on point: “Who kills a man kills a reasonable creature, God’s image... he who destroys a good book, kills reason itself.”

Whether The Jewel of Medina is a good book or not, its loss will be a collective one.