"When the digits darken in my mouth --- heavy eights and nines packed together --- the tense distant faces grow tenser still. When a sudden three emerges from a series of zeroes and sevens, I hear something like a faint collective pant. Silent nods greet my accelerations; warm smiles welcome my slowdowns," he wrote in his book "Thinking in Numbers," which comes out in the United States in July.
At the pi recitation, Tammet realized he had a gift of communicating, and that set him on the path to becoming a full-time writer.
The pi memorization event also led Tammet to Baron-Cohen and colleagues, who made the diagnosis of high-functioning autism. It explained the difficulties he had with communication and social skills as a child.
He has not recited pi since the 2004 event, but still appreciates the beauty and wonder of the number enough to promote Pi Day in France.
"You can find a lover's telephone number. Your date of birth. Your Social Security code. You can find everything in pi," he said. "It's big enough to have all of life inside of it."
Want to memorize pi? Here are 10,000 digits.