Some elements of the exuberant Olympic Games opening ceremony – the drag-queen Last Supper, if that’s what it was, and the Dionysian Papa Smurf – have caused bemusement, ridicule and even outrage. But one thing united the world in awe: the Olympic cauldron.

As the last two torch runners brought the flame into the Tuileries Gardens, by the Louvre, viewers were surprised to see a ring of fire, seven metres in diameter, set under a giant air balloon.