Duddy was initially known in Belfast for his drag queen act, performing in the city's clubs as 'Samantha'. However his initial role in loyalism had been during the late 1970s and early 1980s when he served as the public relations officer for the then legal UDA. Duddy went on to serve as the editor of UDA magazine Ulster for a time and published a book of poetry entitled Concrete Whirlpools of the Mind which received praise for its sensitive treatment of the problems for young working class men drawn into violence. In order to avoid any implication in the Kincora Boys' Home Duddy ended the drag act in 1980 under orders from then UDA leader Andy Tyrie to grow a moustache and drop his voice.
Duddy retired from active loyalism in the 1990s, but was recalled by the UPRG to help rebuild their image after the collapse of the Ulster Democratic Party and the split from Adair and John White. He was the North Belfast representative for the UPRG. At the height of the fall-out in 2003, his home was hit with a pipe bomb. In 2006 shots were fired at his house in Rathcoole, north Belfast; his pet chihuahua "Bambi" died after being hit.
He died in 2007, aged 62, after suffering a massive heart attack. Frankie Gallagher, a spokesman for the UPRG, stated, following Duddy's death: "He came out of retirement to pursue a peaceful path for his community and in pursuit of that he has given his life. It's a massive, massive loss for his community."
He is survived by his second wife, Joyce, and three children.