The effect of taking out leading terrorists is not easy for even so-called experts to predict. So it is with the death, announced by Isis, of Abu Muhammad al-Adnani. head of the external relations and propaganda unit of the ultra-hardline jihadist group and the man who in 2012 announced the creation of a caliphate across Syrian and Iraqi borders. He was targeted in a US air-strike on Tuesday.

As one of the founding members of Isis and a militant with its precursor, al-Qaeda in Iraq, he undoubtedly brought operational know-how to the group. Undoubtedly, too, he has played a potent role in inciting terrorism abroad, both in the west and across the Middle East — although it is less known how significant he was in the logistics behind recent atrocities.

As head of the Isis propaganda machine he was gruesomely effective, his appeals for Isis followers to slay non-Muslims in the west eerily previewed the brutal simplicity of recent attacks, including last month’s mass-casualty seafront killings in Nice in by a fanatic armed with just a truck.