He reached the semi-final of the event beating Ronnie Baxter and Roland Scholten before losing to eventual champion Les Wallace.

[7] In 2004, he claimed his first BDO major title when he won the World Masters in Bridlington, defeating Tony O'Shea 7–6 in the final having trailed 3–5.

[10] His first major final came in the 2000 World Masters where he beat such players as Peter Manley and Colin Monk before eventually narrowly falling to John Walton 2 sets to 3.

[11] King went into the 2002 BDO World Darts Championship as number 4 in the event seedings and reached the final, losing to Australian Tony David.

In 2006, King's form declined and his best result came in the 2006 World Darts Trophy where he made the quarter-finals narrowly losing to Michael van Gerwen 4–5.

[23] He also made only the second round in the 2006 BDO World Darts Championship whitewashing Brian Woods 3 sets to 0 before losing to eventual champion Jelle Klaasen 2–4.

[citation needed] King was angry that rumours had surfaced and even threatened to quit the tournament as the speculation heightened even stating, "I'm really not happy with the treatment I've had today, not just from one person but from a lot of people who I have known for many years".

[27] Having reached the semi-final of the 2007 BDO World Championships losing to eventual champion Martin Adams, King had signed a contract confirming he would play at the 2008 tournament due to a clause in all contracts of BDO players stating that if they reach the semi-finals of the World Championship they are obliged to return the following year, with champions committing themselves to three years.

[34] His performance in the World Championship meant that he moved up to 6 in the PDC Order of Merit and therefore qualified automatically for the 2009 Premier League Darts.

[37] King's successful run in the 2008 Championship League Darts continued into the 2009 tournament as he reached the semi-final before losing to eventual champion Colin Osborne 1–6.

[40] King made a great start to his Premier League career as he opened up with an 8–1 victory over Sky wildcard Wayne Mardle.

Having beaten James Wade, Jelle Klaasen, Wayne Jones and Colin Osborne in earlier rounds, he narrowly lost in the final to Paul Nicholson 13–11.

[49] King lost his last three round-robin matches to Taylor, Raymond van Barneveld and Simon Whitlock, but he still made it to the semi-finals for the second consecutive year, again finishing 4th in the table.

King afterwards admitted he was unhappy with the crowd, as they were loudly booing his starting and finishing doubles, but the £40,000 runner-up prize saw him climb to 13th in the world.

[69] After all 33 ProTour events of 2012 had been played, King was 20th on the Order of Merit, comfortably inside the top 32 who qualified for the Players Championship Finals.

[72][73] His first final of the year came at the eighth UK Open Qualifier in April, having won seven games including defeats over James Wade, Wes Newton and Robert Thornton, but he was then whitewashed 0–6 by Michael van Gerwen.

[74] King reached the final of the Austrian Darts Open by beating Joe Cullen 6–0 in the quarter-finals with an average of 103.66 and Steve Beaton 6–5 in the semis.

[76] King's second European Tour final of the year came in September at the German Darts Masters where he edged past Peter Wright 6–5 in the third round, whitewashed James Wade 6–0 in the quarter-finals and beat Wayne Jones 6–4 in the semis.

[79] King's first final of the year came in February at the Dutch Darts Masters, but he was defeated 6–4 by Michael van Gerwen whilst averaging 107.40.

[84] In a tight match in the quarter-finals of the World Grand Prix, King was defeated in a final leg decider against Van Gerwen as he was unable to checkout 120.

[86] King continued his fine form at the Masters by beating Simon Whitlock and Justin Pipe and then produced a superb performance to exact revenge over Van Gerwen 11–9 with a 121 finish on the bull.

[87] The misses didn't seem to affect him at the Grand Slam, as he punished every mistake from Gary Anderson in a second round 10–4 win and then beat Stephen Bunting 16–9 to face Phil Taylor in the semi-finals.

[93] He then overturned an 8–5 deficit against Nathan Derry to win 9–8 and emerged successfully from a deciding leg for the third game in a row by beating Kyle Anderson 9–8 to reach the quarter-finals.

[100] King inflicted James Wade's first ever first round defeat at the World Matchplay by beating him 10–5 and then saw off Brendan Dolan 11–8 to play in the quarter-finals of the event for the first time in seven years.

[101] In an extremely tight match he narrowly lost 16–14 to Phil Taylor, with the 16-time world champion stating that it was the best he had seen King play for two or three years.

He reached the quarter-finals of the World Matchplay, beating defending champion Gary Anderson en route, before losing to Michael Smith.

At the 2022 World Championship, King had his best run since 2009 by beating Ryan Joyce, Steve Lennon and Raymond Smith, but was eventually whitewashed 5–0 in the quarterfinals by James Wade.

During his run he beat Rick Hofstra 3–1, Jarkko Komula 3–2, Ritchie Davies 5–4, Tony O'Shea 5–1, before meeting Andy Fordham in the final.

[citation needed] King is good friends with and lives close to fellow darts player Peter Wright and they often practise together.

He is also a keen motor enthusiast and revealed that when younger he gave up his chance of becoming a racing driver to continue his fledgling darts career.