Vengeance is the darkest of human emotions. It is the belief that any injury that a person deals to you must be returned in kind. At its worst, it leads to feuds and atrocities; reprisals on top of reprisals. The Troubles in Northern Ireland could have ended so much sooner had it not been on for the desperation of either side to let no slight go unpunished. Yet for all this, it is surprisingly common for it to be glorified in the most unlikely of places.