Retired Garda chief reveals bringing down Larry Dunne was greatest achievement during colourful career 14 Dec 2020, 7:30 A RETIRED Garda chief has told how bringing down Larry Dunne was his greatest achievement during his colourful career. Former Assistant Commissioner Michael O’Sullivan was one of Ireland’s first undercover detectives as part of a unit known as the ‘Mockies’. 4 4 4 Dunne at court in 1985Credit: RollingNews.ie The Mockies — a group of young cops dressed to look like drug addicts — was set up in the early Eighties as Dublin fell into a heroin epidemic. Dunne was responsible for bringing smack to Ireland and became the undercover unit’s chief target as they sought to bring justice to the thousands of families who had been affected by the drug scourge.