STOCKSHOTS of Londonderry, known as "Derry" by nationalists and among the city's Catholic community, in Northern Ireland, where the "Bloody Sunday" massacre took place over 50 years ago, a crucial moment which turned much of the city's Catholic population against British troops sent there to end sectarian strife. "Bloody Sunday" is one of the most painful episodes of the "Troubles", the three decades of violence between nationalist and unionist communities that ended with the Good Friday Agreement signed 25 years ago. STOCKSHOTS