Peter Nicol is one of the greatest athletes that Scotland has produced.

He was world champion in 1999, won four Commonwealth gold medals and was world No.1 for 60 months, making him undoubtedly one of the greatest squash players of all time. Mention his name in his home country, though, and, almost without exception, he is remembered for being "the guy who defected to England".

Of all nationality switches, few would attract quite as much vitriol. In March 2001, Nicol, from Inverurie, announced that he was changing allegiance from Scotland, the country in which he was born and bred, to the Auld Enemy. At the height of his career, he defected to England because of what he felt was a lack of support being offered by Scotland, believing that England, by contrast, would provide him with the resources he felt necessary for him to remain the best player in the world.

Nicol's decision was decried in the land of his birth; he was called a traitor and his defection was viewed as an unforgivable betrayal by many. Thirteen years on, Nicol is retired from the sport and lives in New York with his wife and young son, having founded the Nicol Champions Academy where he coaches young players.

The 40 year-old admits he has mellowed since his retirement from professional squash in 2006 but he remains adamant that his most notorious decision was, without doubt, the right one for him. "It was the best professional decision of my life," he said. "I've never had any regrets, not one."

Nicol travelled to the Commonwealth Games in Kuala Lumpur in 1998 as world No.1 and won the sport's first Commonwealth gold medal, for Scotland, in the men's singles, as well as a bronze in the men's doubles. He became world champion a year later. It was deemed by the Scottish authorities at the time that Nicol was earning so much through his success that he was not eligible for any central funding. "My argument was that it shouldn't matter what I was earning because most of it was being spent on my sport and on trying to make myself a better player," said Nicol. "I remember being really happy that I had reached the semi-finals of a tournament in Hong Kong because it meant that I had broken even. Considering that the whole purpose of funding was to produce the best in the world, and then keep the people who have achieved this at the top, it [the denial of central funding] just seemed ludicrous."

Nicol admits that, as with so many athletes at the top of their sport, he was selfish and that his decision to defect to England was a selfish one. "I had lived in England since I was 17 and it was the most logical decision, as well as being the best thing for my game," he reflected. None of this meant that it was an easy choice to make, though. "It did take a lot of soul-searching. I had a lot of long conversations; the final one was with my father who is a very proud Scot," Nicol said. "It was tough when I made the decision. It was tough to hear some of the things that were being said and I got a few letters which weren't very complimentary, to say the least."

Nicol believes that some of his greatest attributes on a squash court were what got him through this turbulent time. He could, he says, switch his emotions off when he went on court, becoming "this different animal".

"Looking back, I couldn't be that person now because I'm too emotional, too interested in other things, but, at the time, it was all so simple. I just wanted to do whatever was needed to be the best player that I could be," he said. "I feel sad that I had to do it though. It was something that someone shouldn't have to do."

This single aspect of Nicol's career has perhaps overshadowed his remarkable list of achievements. His rivalry with the Canadian Jonathon Power was one of the most acclaimed the sport has known. It was Power whom Nicol beat to win his Commonwealth gold in 1998 in one of the sport's greatest matches. Nicol had lost his previous six contests with Power and believes that if he had not defeated the Canadian that day, he might well have lost the next 15 encounters. Power was Nicol's antithesis. While Nicol is softly spoken and unassuming, Power would sledge him relentlessly and use his physical presence to disrupt the game, often barging his rival with a shoulder. "He was a little s**t, basically," says Nicol, "but he was like John McEnroe [in that] he played better when he was behaving like that. But I became a far better player because of him."

Of all the ups and downs throughout his career, of all the victories, the titles and the accolades, Nicol selects an unlikely accomplishment as his proudest achievement. "The single thing that I'm most proud of is that I was [ranked] in the top 10 in the world for 12½ years straight," he said. "And I only dropped out because I retired."