For 17-year-old Mary Amanuel, from London, it happened in Tesco. "We were in year 7," she remembers, "and my friend had made an Instagram account. As we were buying stuff, she was counting the amounts of likes she'd got on a post. 'Oooh, 40 likes. 42 likes.' I just thought: 'This is ridiculous.'"

Isabelle, an 18-year-old student from Bedfordshire who doesn't want to disclose her surname, turned against social media when her classmates became zombified. "Everyone switched off from conversation. It became: 'Can I have your number to text you?' Something got lost in terms of speaking face to face. And I thought: 'I don't really want to be swept up in that.'" For 15-year-old Emily Sharp, from Staines in Surrey, watching bullying online was the final straw. "It wasn't nice. That deterred me from using it."