Millions tuned in to see KSI beat Joe Weller in the biggest amateur boxing match of all time. But what didn't they see? The blood, sweat and determination underpinning KSI's intense training regime and a revealing look at his world off camera. This is the exclusive and never before seen story of Knowledge, Strength and Integrity, and how JJ, with 18m YouTube subscribers, went from actor to athlete.

Is being a Youtuber a viable career option? How realistic is being a Youtuber as a full-term career? Dan Howell investigates. Dan Howell meets Dan Rhodes and Vikkstar to question whether being a YouTuber is a viable long-term career. Exclusive data analysis shows just how hard it is to keep making successful content.