At 150, according to Dunbar’s original research – and borne out by subsequent studies – human groups begin to struggle to maintain cohesion. Each individual, according to the theory, has to understand every member of the group’s relationship with every other member.

But in an age where the internet acts as a force-multiplier for sociability (if only for those who are native to it), it is now possible to develop friendships with people we’ve never met at all. Twitter is more than just a conversation; it is a schoolyard, a lunchroom, a water cooler. “Internet friends” are still friends – at least as much as “friends” on Facebook who we haven’t seen in years.

I found out that my friend had died late at night, and reflexively direct-messaged her boyfriend on Twitter. The next morning, I wasn’t sure if I’d made a mistake: I was a stranger to them, really. Did mutual following one another on Twitter – the fact that I read their streams of consciousness, and they mine – mean anything to them? What did it mean to me? Was it acceptable or unwelcome that, in his time of grief, I’d inserted myself like there was anything comparable in our experiences of her life?