Both surveys found that women averaged more online friends than men, counting 166 compared with 145 in one survey and 196 to 157 in the other. Overall, participants in the first survey reported that of their online friends, they regarded just 28 per cent as genuine and would turn to only four for help. The second group, with slightly higher numbers of online friends, said they would turn to 14.

“There is a cognitive constraint on the size of social networks that even the communication advantages of online media are unable to overcome,” Dunbar said of the figures.

“The fact that people do not seem to use social media to increase the size of their social circles suggests that social media may function mainly to prevent friendships decaying over time in the absence of opportunities for face-to-face contact.”

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Forget Facebook friends: this is the (small) amount of people you can rely on in a crisis