When "A" shares of Berkshire Hathaway broke through $100,000 in October, investors were reminded of Warren Buffett's remarkable management record. Over the past 40 years, Berkshire has generated annualised returns that have been more than twice those of the S&P 500.

At the same time, it brought attention to a rarely discussed investment structure - the holding company, and its capacity for delivering diversified and profitable exposure as well as many mutual funds.