I have no idea what it’s like to live in a young offenders’ prison like the notorious Feltham but I’m going to go out on a limb and guess that the arrival of Crime TV veteran Roger Graef, poet Simon Armitage, pioneer documentary director Brian Hill and Channel 4 to make a ‘documentary musical’ in which the prisoners themselves, their wardens and counsellors perform rap tunes about their lives and aspirations made a dent in the routine. The result, Feltham Sings, shown on Channel 4 tonight, was chilling and moving and often surreal (a particularly disturbed boy rapped about suicide while two of his warders sang a chorus about paracetamol) and reminded me of what Channel 4 was invented for.