For the purposes of my story, I have the two events occurring on the same day when in fact they probably took place two or three months apart. Nevertheless, together they dealt the death blow to Maslama’s giddy dreams of absolute victory. In mid-August 717, what was left of the Arab fleet evacuated the miserable remains of Maslama’s army. Alas, their troubles were not over. A terrible storm engulfed the fleet and only five vessels survived the voyage home. The expedition’s failure was total and abject. No small wonder that the Byzantine chroniclers attributed the successful defence of the city to the providence of God.

Although wars between the two empires continued, the Arabs never again made an attempt to knock out Constantinople, and no historian, ancient or modern, denies that the repulse of the Arab advance at the doorstep of mainland Europe marked a decisive moment in that continent’s history. It should be added that eventually Arab and Byzantine reached an accommodation with each other, settling into an uneasy coexistence for the next three or four centuries. It took the encroachment of an outsider people – the Seljuk Turks – to upset the balance once again and stir up renewed animosity between Christian and Muslim. In time this development was answered by other outsiders from the West, the Latins, in the form of the first Crusades. This, some four hundred years after the astonishing gains of the early Muslim conquests.

As to the efficacy of Greek fire, any interested readers can find a reconstruction of the Byzantines’ secret weapon (by historian Richard Windley) on YouTube – both in its syphon form and as a primitive kind of hand grenade. Although the exact methodology and formulation of the substance that created Greek fire is a secret lost to history, the reconstruction represents something pretty similar, and demonstrates without any doubt how effective technology very like it could be.