Experts at the special gangs unit in east London give us their take on drill and we return to Yusuf's story. It’s been a fortnight since we first met him – but has he changed his ways?

Presented by Tracy Ollerenshaw. Drugs, Drill and Doing Time is a four-part series that follows the story of 17-year-old Yusuf, a notorious London gang member who's facing jail for carrying a knife and acid.

Produced by Tracy Ollerenshaw, Toby Sealey and Will Chalk.