Book excerpt: Barlinnie is one of the most notorious prisons in the world and for a hundred years it has held Glasgow's toughest and most violent men, swept up from the city streets. Ten men died on its gallows in the infamous Hanging Shed, including serial killer Peter Manuel. It has sparked rooftop protests and cell block riots, and been home to godfathers of crime like Arthur Thompson Snr and Walter Norval. Barlinnie was also the scene of one of the most controversial experiments in penal history, the Special Unit, where the likes of Jimmy Boyle and Hugh Collins were at the centre of a fierce battle between those who see prison as retribution and those who regard it as a step on the road to redemption, even for the most evil killers. Paul Ferris, T C Campbell and gangleaders galore have languished behind its grim walls and, a hundred years on, Barlinnie still makes headlines. This is its fascinating, turbulent story.