Between 1996 and 1999, O'Sullivan reached three world semi-finals in four years. At the 1997 World Championship, he achieved his first maximum break in professional competition; compiled in a time of 5 minutes and 8 seconds, it remains the fastest competitive maximum break in snooker history. He won his second UK title later that year at the 1997 UK Championship. Despite these successes, his career also became marred by controversy in the later 1990s. During the 1996 World Championship, he assaulted an assistant press officer, for which he received a suspended two-year ban and a £20,000 fine. After winning the 1998 Irish Masters, he was stripped of his title and prize money when a post-match drug test found evidence of cannabis in his system. O'Sullivan subsequently acknowledged frequent abuse of drugs and alcohol in the early years of his career, which resulted in spells in the Priory Hospital for rehabilitation.