The New Zealander also contributed to his team's commanding victory over France, while Britain confounded the gloomy forecasts with spirited performances that left them as team bronze medallists.
Tait, fourth overnight, would have been happy to settle for an individual medal of any colour when he woke up yesterday. "There were three people ahead of me and I thought they'd all go well," he said.
But Germany's Bettina Overesch dropped out when Watermill Stream, who was lying second, failed the final horse inspection. Two show jumping errors apiece from Australia's Stuart Tinney on Jeepster and Mark Todd, the overnight leader on Broadcast News who hit the second and third fences, eventually gave Tait his unexpected title.
Todd, who was runner-up, has won every other major championship in the sport but the world title continues to elude him. "This is my fifth attempt and it's by far my best result so far," he said.
Britain was represented by a quartet that some had described as "The C Team" after a series of set-backs to key horses. They lost their most experienced rider, Karen Dixon, who retired Too Smart after the horse had tired and fallen on the cross-country. But the other three - Gary Parsonage on Magic Rogue, Polly Phillipps on Coral Cove and Nigel Taylor on the Frenchman II - had all jumped clear within the optimum time, which gave them the best team cross-country score.
On Saturday morning Giles Rowsell, chef d'equipe of the British team, had been angered to learn that the 17th cross-country fence (involving a double of corners if jumped by the quickest route) had been left off the course after heavy overnight rain. The decision, taken on the advice of the technical delegate Hugh Thomas, meant the British riders had less opportunity to advance from seventh place after the dressage.
Despite those three superb rounds, they were only fifth in the morning before Australia dropped out when David Green's Chatsby failed the inspection. A clear round from Parsonage and one jumping error each from Taylor and Phillipps was good enough to put Britain ahead of the United States.
Results, Digest, page 26