It comes after teenagers arranged to meet in Clapham, south London, in the last week as part of “link-ups”, using social media apps including TikTok and Snapchat

It comes after teenagers arranged to meet in Clapham, south London, in the last week as part of “link-ups”, using social media apps including TikTok and Snapchat

Bosses write to home secretary and London mayor listing series of incidents staff have faced in past week