[2] Duddy ran a fish and chip shop in the late 1960s which was supplied with beef burgers, from a supplier whose van driver was Martin McGuinness.
After thirteen unarmed civil rights marchers were shot dead by British Parachute Regiment troops in what became known as Bloody Sunday, Duddy warned Lagan: "This is absolutely catastrophic.
"[5] In the aftermath of the events and repercussions of Bloody Sunday, MI6 agent Michael Oatley arrived in Belfast in 1973, seeking to understand the situation in Northern Ireland and hopefully create a communications channel between the IRA and the British Government.
[6] Duddy and Oatley were the main channel of communications between the British Government and the IRA leadership during the 1981 Irish hunger strike.
Over the period of 4–6 July 1981 they exchanged many telephone calls, with Duddy urging the "utmost haste" on the part of the British, because "the situation would be irreparably damaged if a hunger striker died".
After the end of The Troubles, Duddy served as a member of the Northern Ireland Policing Board and helped broker negotiations related to the marching season.