For one thing, there was the gravity of the occasion. As Syrian government troops, backed by Russia and Iran, complete their final stranglehold on what remains of rebel-held Aleppo, she reminded us that even in the midst of Syria's five long years of atrocities, this was something of a milestone: an episode that future generations would regret not stopping, like Srebrenica or Rwanda.

Then there was the language. Rather than the turgid diplomatic innuendo so often used at the UN security council, Power accused Syria, Russia and Iran head on of putting tens of thousands of people in an "ever-tightening noose". As she put it: "Is there literally nothing that can shame you?"