For many, the ethnicity and heritage of Ali Harbi Ali were wholly irrelevant to his alleged behaviour. Acknowledging that Ali is of Somali background, we were told, is racist and xenophobic. He must only be identified as British.

As someone who was born in Somalia, I find this absurd. Of course a suspect is not a murderer because he has a Somali background. But denouncing facts as racist — especially when the person in question was referred to Prevent, and police and security services believe he may have been inspired by al-Shabaab in Somalia — forces a dangerous ignorance on the public.

Yet it is just one of a number of fallacies that continue to dominate almost every discussion about Islamist-driven terrorism — fallacies that are promoted by both the media and British authorities. Indeed, it strikes me that our efforts to counter Islamist attacks are hindered by at least three other misconceptions: our insistence on describing a perpetrator as a “lone wolf”, our obsession with online self-radicalisation, and the idea that “all extremisms are created equal”.

Take that first fallacy. As unpleasant as it may be to acknowledge, I suspect Sir David might be alive today, along with numerous other victims of Islamist extremists, if those in charge of preventing terrorism recognised that Islamist extremists are anything but lone wolves.