King has reached two World Championship finals and four semi-finals since making his debut in the BDO version in 1997. He went as far as the semi-final in his debut year, losing to eventual champion Les Wallace. During his run he hit thirty 180s, setting a new record for the tournament at the time. Since switching to the PDC, his best performance came in the 2009 World Championship when he reached the semi-final, losing 2–6 to Phil Taylor.