President Emmanuel Macron was surveying a glacier in the French Alps on a visit in February when an aide forwarded a video that had just been posted online, showing his choice for Paris mayor masturbating.

Benjamin Griveaux's campaign was already floundering, a month out from the first round of the election, and his naiveté in falling for a simple sting meant Macron had to choose: back a loyal and trusted ally, or sack him.