On September 1, Justin Kelly becomes the 22nd person to hold the office of commissioner of An Garda Síochána. Confident, keen-eyed, fit and energetic, the 53-year-old Dubliner will take on one of the most challenging jobs in the public service at this time. The commissioner of An Garda Síochána has a dual role that is not widely understood. The force that he (or she) leads is both the national police service and the lead agency in State security. Ireland is the only country in the world where policing and security are vested in the same agency. There is no MI5…