BDO career

He started his career before the game split into two separate organisations during the early 1990s. He accumulated many Open tournament titles including the Belgian Open (1991, 1992), Denmark Open (1991, 1992), French Open (1991, 1993) and the Swedish Open (1991). Harrington's 1991 Winmau World Masters victory over Phil Taylor remains one of Taylor's rare major final defeats – although Taylor was only a one-time World Champion at the time and had lost his world crown to Dennis Priestley in January 1991.

Harrington made his World Championship debut in 1992, reaching the quarter-finals before losing to eventual runner-up Mike Gregory. At the 1993 World Championship, Harrington was seeded fourth but lost 2–3 to Wayne Weening in the first round. After those championships, the majority of the top players left the governing body, the British Darts Organisation, to form the WDC (now PDC) in an acrimonious split in the game.

PDC career

After the WDC/PDC started their own World Championship in 1994, Harrington would be ever-present in the event for the first ten years. He reached the quarter-finals in the inaugural tournament, but his best ever achievement came in the 1995 World Championship – by reaching the final. He lost the final 2–6 to Taylor, who was winning the third of his world championship titles at the time.

He reached the World semi-finals on two further occasions, 1998 (where he was beaten by that year's eventual winner, Taylor) and 2001 (where he lost to that year's runner-up, John Part) and the quarter-finals in 1997. However, after the 2002 World Championship (where he was seeded third), his form slumped dramatically to the point where he was outside the top 16 by 2003 – and a first round defeat by Alan Warriner would turn out to be his last appearance in the World Championship.

He did have some success at the other major PDC tournaments. In 1998, he beat Ronnie Baxter in the final of the World Matchplay, helped along the way by his now famous 125 checkout (Treble 15, Double 20, Double 20); he then successfully defended the title in 1999 with a victory over Peter Manley. He and Phil Taylor remained the only players to retain a major PDC title until Raymond van Barneveld retained his UK Open title in 2007. Harrington also reached the final of the first World Grand Prix event in 1998 losing to Taylor. Along with Richie Burnett he also reached the final of the PDC World Pairs tournament in 1997, losing in the final to the pairing of van Barneveld and Roland Scholten.

Final years

After three knee operations in the first half of 2001, Harrington's form dropped dramatically, although he never officially announced a retirement from the game. He still attempted to qualify for the major UK tournaments until the 2007 World Championship – where he lost in the first qualifying round. He is unranked in the official Order of Merit. Harrington retired from professional darts in 2007, and has never thrown another dart in any competition since.

Harrington became a director of the PDC and now also regularly acts in the capacity of a commentator and analyst on Sky Sports' live darts coverage. At one time, he was also the manager of former PDC world number one Colin Lloyd.

BDO

• 1992: Quarter-finals (lost to Mike Gregory 3–4)
• 1993: 1st round (lost to Wayne Weening 2–3)

PDC

• 1994: Quarter-finals (lost to Peter Evison 1–4)
• 1995: Runner-up (lost to Phil Taylor 2–6)
• 1996: Group stage (beat Nigel Justice 3–0, lost to Larry Butler 2–3)
• 1997: Quarter-finals (lost to Dennis Priestley 2–5)
• 1998: Semi-finals (lost to Phil Taylor 2–5), (beat Keith Deller for third place 4–1)
• 1999: 2nd round (lost to Shayne Burgess 1–3)
• 2000: 1st round (lost to John Lowe 2–3)
• 2001: Semi-finals (lost to John Part 5–6)
• 2002: 2nd round (lost to Dennis Priestley 3–6)
• 2003: 2nd round (lost to Alan Warriner-Little 2–4)

BDO major finals: 1 (1 title)

Outcome	No.	Year	Championship	Opponent in the final	Score
Winner	1.	1991	Winmau World Masters	Phil Taylor	3–2 (s)

PDC major finals: 4 (2 titles, 2 runners-up)

Outcome	No.	Year	Championship	Opponent in the final	Score
Runner-up	1.	1995	World Darts Championship	Phil Taylor	2–6 (s)
Winner	1.	1998	World Matchplay	Ronnie Baxter	19–17 (l)
Runner-up	2.	1998	World Grand Prix	Phil Taylor	8–13 (s)
Winner	2.	1999	World Matchplay	Peter Manley	19–17 (l)