The garage of Wigg's picturesque house in one of the more remote parts of Buckinghamshire shows all the signs of a profession vacated in a hurry. One bike is still on its stand, where Wigg was preparing it for a winter season in Australia, another is propped against a wooden bench in the corner. Overalls hang off the beams, tools lie untouched since the afternoon of 8 November.
Wigg recalls the day. "I was dashing about like a madman. I was trying to get these bikes ready for shipment and it was my wedding anniversary so I was wondering where to take my wife for dinner that night. Then the lad who mows the lawn came over and told me the mower had packed up. That was pretty well the last thing I remember. The next thing I knew I was waking up in Milton Keynes General Hospital the following evening."
The cause of epilepsy, particularly in adults, is the subject of intense medical debate. But the natural buffeting that comes with the territory is a reasonable starting point for its diagnosis in a speedway rider. Towards the end of last season, Wigg suffered a series of bad falls, the most damaging of them in August on his home track at King's Lynn, when he was catapulted over the handlebars, hit a wooden fence - a safety fence, they call it - head first and suffered concussion.
In a lifetime of accidents, this seemed just another minor dent and Wigg thought no more about it until that afternoon of 8 November. Even then, the full implications of his seizure did not hit home. Wigg and his wife Charlie went to Australia on holiday. The morning they were due to fly back, Wigg suffered another attack, not as long as the first, but equally intense. What he also realised subsequently was that between 8 November and 28 January, he had experienced the symptoms of other fits, the haziness and the incoherence, without recognising them. "Once I was in the estate agents and just began talking gibberish."
Wigg's celebrity in Britain has been confined largely to the champions' dustbin of clips on the BBC Sports Personality of the Year - "And Simon Wigg won his fifth world title..." His career has coincided with a downturn in the fortunes of British speedway and his five world championships have been won in the long-track discipline which attracts crowds of 50,000 to circuits in Germany, Poland and the Czech Republic but has little traditional following here.
But 18 seasons in the British league, countless cheerless evenings spent in raucous and dangerous pursuit of league points, have brought "Wiggy" a strong following among the dwindling band of dedicated speedway supporters. Wigg could be relied on to get stuck in, one reason why a star-studded cast and, weather permitting, a large crowd will attend his testimonial at Oxford Stadium this afternoon.
Six world champions will line up, including Hans Nielsen, who will return to the club where he and Wigg won three successive national speedway titles. "It's been one of the unexpected rewards of this whole thing," Wigg says. "The riders all said `yes' before I'd finished asking them the question."
Wigg bills the day as his farewell to British speedway, but, in his heart, he probably knows it could be more terminal than that. The details of organisation have provided a convenient outlet for his energy. His mind has not had the time to confront the realities of the new life he has already dubbed Phase Two. But he has not had to search far inside a brutal profession for reasons to be cheerful. One of the first riders to call him when news of his epilepsy came out was Erik Gundersen. "He was world champion in the mid-Eighties, but had a very bad accident in the World Team Cup final in 1989. First reports said that he wasn't going to live, but he got through and then he struggled to regain any sort of fitness. He walks with a bit of a shuffle and he can't use his left hand properly, but he's been remarkable in the way he's got back on with his life and not let it bother him.
"Per Jonsson, another world champion, is paralysed after crashing in a league match in Poland. There wasn't a speedway rider in the world who wasn't hit hard by that. I've had my low moments, but I've got a great wife and children [Abigail and Ricky] and my in-laws are brilliant. Compared to Per and Eric, top blokes like that, my situation doesn't seem so bad, to be honest with you."
His own experiences lend depth to that robust philosophy. In Italy, nine years ago, Wigg was hurled backwards off his bike on to his neck while testing a new clutch for an Italian manufacturer. They fixed him with a neck brace, but he took it off that night to go to a club. A week later the pain was so acute he was sent for some X-rays by his physio. "I was standing waiting for the results when the nurse came running over with the X-rays and said `Don't move'. The doctors put a brace around my neck while I stood there. I'd broken the third and fourth bone in my vertebrae and my spinal cord was rubbing between the two. If I'd tripped up, fallen over, even turned my head too quickly, the cord would have snapped and I would have been paralysed. I'd ridden two races on the Sunday, with a broken neck. I mean, I can laugh about it now, but it doesn't bear thinking about." He was out for six months.
Equally bewildering was a controversy over a drugs test after a victory in the world title in Germany six years ago. Under International Olympic Committee regulations, Wigg's routine post-race test was negative. But his sample was deemed positive for caffeine by the IOC's flagship laboratory in Koln. Wigg was disqualified and a German rider claimed the title.
Later, it was discovered that Wigg's caffeine level had been arbitrarily and illegally recalculated by Manfred Donike, then head of the Koln Institute and one of the most influential drug-testers within the Olympic movement. Wigg was reinstated, but the tottering integrity of the IOC's testing procedures was dealt another damaging blow. Wigg is still mystified by the whole frustrating saga. But the following season he had the words "Caffeine Frei" (Caffeine Free) emblazoned on the back of his leathers.
Tomorrow morning, when the familiar acrid smell has drifted away and the decibels have died, Wigg will need all his considerable resolution to contemplate the future. No one with his history of comebacks can be consigned to retirement lightly, but if a non-descript track in Kent did host his last ride in early November, Wigg does not have to travel far to relive an extraordinarily prolific career. His study is papered floor to ceiling with trophies. He knows the story of each one.
"I started riding when I was 14, I've been riding for 25 years and if I never ride again, I won't be going out with anything like what the Giggses and Beckhams have stashed away, but I've had the satisfaction of doing what I wanted to do every day, which is worth so much more than money. Although I've been warned I might have to stop, I don't really take it seriously. I've not even thought what an emotional day Sunday might be, let alone what happens then. I haven't a clue what I'll do."