None of the Islamist organisations named above is, so far as I know, actively engaged in promoting violence in this country, but all of them preach extremism which creates the mental space in which violence can breed.

For years, David Cameron has been pushing this point, but the bureaucratic response is agonisingly slow. The website of MI5 still emphasises that, since the Cold War, “we no longer undertake counter-subversion work”. Instead they concentrate on terrorism. Goodness knows, there is a need to head off actual plots, and MI5 should be congratulated for its success, but one reason we won the Cold War was because we understood what, ideologically, we were up against. The ideological content of Islamism is even more important than was that of latter-day Soviet Communism, and much more persuasive within a section of the British population.

The Security Service Act of 1989 allows MI5 to investigate attempts to “undermine parliamentary democracy” by “political” means as well as violent ones. Islamism is, by self-definition, a political attempt to undermine parliamentary democracy, yet is largely unstudied. If our own spies won’t do it, who can? Public bodies dealing with Muslim organisations are, therefore, fighting blind, having few means of telling the good guys from the bad.

Ultimately, the capacity of a civilisation to resist those who hate it depends on its self-belief. In Europe, this was expressed in what was called Christendom, enriched by the ideas of the Enlightenment. The founders of the European Union wanted it to give Christendom modern democratic form, but this is now nearly invisible. The leader of the union’s largest Christian Democrat party, Angela Merkel, has let more than a million mainly Muslim immigrants into her country this year alone. The East German pastor’s daughter is surely a much nicer person than Donald J Trump, but I wonder if she is not doing more actual harm to the future of the West.