Juan Pablo Montoya decided to quit Williams after an extraordinary row with the team at last year's French Grand Prix, technical director Patrick Head has revealed.
Explaining the full extent of the bust-up, Head told reporters at the Williams factory how the Colombian, who joins rivals McLaren at the end of the season, lost his cool in the Magny-Cours race on July 6th. He said Montoya launched a tirade of abuse at team members over the car radio for 10 minutes before sulking and then slowing down.
He was then reprimanded at a meeting on the following Wednesday.
"I think Juan was not impressed at having his knuckles rapped and I know the decision to sign with McLaren was taken within a few days of that," added Head.
The row was triggered by a pitstop when Montoya, chasing team mate Ralf Schumacher, thought the German had been given preferential treatment.
"Juan incorrectly thought that we had notified Ralf of his actions and called Ralf in one lap early. So he was pretty strong on the radio abusing the team verbally for the next 10 minutes," he said. "And then I think he went into a bit of a sulk and backed off and cruised to the end of the race and maybe finished 15 or 20 seconds behind Ralf.
"In fact as it happened in that last bit of the race, Ralf made a bit of an error and slipped wide. Had Juan been on his tail he probably could have taken advantage of it."
Montoya admitted at the launch of the new Williams last month that he had disagreements with the team and that there had been certain incidents. The fact that he was paid less also grated, although Montoya said he had not decided to move for the money.
Head, who praised Montoya as a future champion with superlative driving skills, said the Colombian had never found it easy to finish behind his team mate.
"Finishing second behind his team mate does not make him a happy lad," he said. "Juan is a passionate character and by virtue of that he sometimes makes impulsive decisions and comes to impulsive conclusions.
"He's probably not perfect but I expect he will win championships in his time."
Team boss Frank Williams said he was sorry to lose the Colombian who won twice last year and challenged for the title until the penultimate round.
"He's a great talent and we're sad to see him go," he said.