Northern Ireland is a changed place. Few are better positioned to notice that change than Martin Dillon. Dillon is one of the most important chroniclers of the north. For more than 50 years he has been investigating the worst of events. His books have been essential in understanding the Troubles from the Shankill Butchers to the disappearance of Jean McConville.  Dillon established sources who were second to none. His detailing of the claustrophobic, suffocating and suspicious world of double agents, informants and double-crossing in his book Dirty War led the way in showing the conflict for what it was. He…