Does this herald the beginning of the end for Isil, which has spread dramatically since June? Or, as Sir Nick Houghton-the UK’s Chief of the Defence Staff- warned, will Isil simply “regenerate leadership” and bounce back?

First, the academic literature suggests that a strategy of killing leaders – ironically, given Isil's depredations, known as decapitation – may be effective only in a narrow range of circumstances.

Second, Isil is accustomed to this. It is an organisation that was forged under far greater pressure on its leadership than exists today. In its earlier incarnation, as Al Qaida in Iraq (AQI), it was subject to an unprecedented barrage.

Its founding leader, Abu Musab al-Zarqawi, was killed in 2006, and many of his successors thereafter. Indeed, the rapid death of his superiors is how Baghdadi himself – a relatively junior figure a decade ago – rose through the ranks so fast.

Also, Baghdadi has, under him, at least 12 local rulers, a three-man “war cabinet”, and eight leaders who “manage portfolios like finance, prisoners and recruitment”. Under wartime conditions.

But it is not yet known what will happen if Al-Baghdadi is killed.