One of the many mementos that litter Warren Buffett's office is his first ever tax return. It was filed when he was just 13 years old. By then, he’d read every book about investing in the Omaha Public Library and had launched a number of businesses including a horse-racing handicapping sheet and four paper rounds.

This is according to journalist Bethany McLean, who has just penned a profile of the octogenarian founder of Berkshire Hathaway in this month's Vanity Fair.