At least 34 teenagers were stabbed to death last year in the UK. In just a decade, the number sentenced for carrying a knife has risen ten-fold. Panorama's Raphael Rowe goes inside prisons to gain rare access to those responsible - the young offenders convicted of carrying, using or even killing with a knife. Interviewing them in their cells, the programme provides a thoughtful and sobering insight into the lives and minds of those at the centre of a highly-charged national debate.