About a year ago a friend of mine tried to tip me about a nascent boom in diamond prices and diamond mine stocks. I barely managed to feign interest. Along with many others, I associated diamond mining with a near cartel and sleazy scam artists.

Three years earlier, James Passin, the managing partner of the $550m Firebird Global Fund, a New York hedge fund, thought the same way. “I’d been looking around for commodities other than oil, copper, or gold. I’d written off diamonds as a [market] manipulated by De Beers.” The stain of a monopoly preserved by giant hidden reserves kept off the market was reinforced by pulp fiction, US Justice Department action, civil suit claims, and historical fact (US v DeBeers Centenary AG, 11 Harrowhouse).