Terrible news. Tom was a strong character, in some eyes a rebel and a borderline troublemaker with his at times very clever (and at times also very naughty) observation of racing rules, but his impact on racing in a number of series was tremendous.
Although he was latterly better known for his controversial days in F1 at Benetton (taking Schumacher from Jordan and several skirmishes with the FIA, including the pitlane fire at Germany), for many people it will be the success he brought for Jaguar back in the 80's (and employing some young bloke called Ross Brawn at the time) that wil be the stand-out period. From Silverstone to Le Mans to Bathurst, Walkinshaw stamped the Jaguar name firmly back into the forefront of saloon and sportscar racing, bringing them series wins after a 30 year absence.
He was a tidy racer himself, often getting behind the wheel of the racing XJ-S and setting some mean times in his own right. Here's a clip of him tearing round the mountain 25 years ago.
[media]http://www.youtube.com/watch?v=M9I7GWllPFY[/media]
Deepest sympathies to his family, and all the best Tom. You'll be sorely missed.