I have to admit to a real feeling of shame as I write these words: the shame at the fear I felt in expressing my solidarity for my fellow journalists at Charlie Hebdo.

The terrorists who killed 12 people at the French satirical magazine this week have ushered in a horrible new reality. Everyone who has dared to criticise or ridicule extremist Islam is now a target for terrorists.

Across Twitter and Facebook people are replacing their profile photos with the words Je Suis Charlie or the hashtag #jesuischarlie. Are they targets, too? If so, what nightmare world are we entering?

I can't speak for others, but my guess is that, around the world, journalists hesitated before voicing their support for Charlie Hebdo. Such is the state of freedom of speech in the face of Islamist ultraviolence.

At the beginning of the 1990s, I made Paris my home for three years. This was at the height of the last wave of terrorist attacks there, when the civil war between the Algerian regime and Islamist rebels arrived on the streets of the capital.

The events sparked a lifelong interest in Islam. I spent hours at the Institute du Monde Arabe on the banks of the Seine and the tea room of the Paris mosque. I interviewed Algerian dissidents to come to a greater understanding of the conflict.

When I returned to London, I spent three years studying the origins of the Muslim faith and the history of Islam. I interviewed Islamists across Britain in an attempt to understand the modern jihadist phenomenon.

Does any of this help me to explain what happened in Paris: where individual cartoonists and journalists were targeted for summary execution in the name of Allah?

Perhaps, a little. Like many a totalitarian ideology, the Islamist death cult is designed to defy rational explanation and induce a feeling of desperation and hopelessness in its opponents. And, yes, fear.

These are feelings the Jewish community of France knows all too well as it struggles to deal with growing Gallic antisemitsm.

But these are the feelings we must resist in our unquestioning solidarity for the Charlie Hebdo team.

Despite everything, my fascination for Islam that began a quarter of a century ago remains undimmed. This is my small victory over the fear and shame.