Eight months ago, a former business journalist working from a modest London apartment on the south bank of the Thames, David Robertson, penned a three-page letter to the Australian Securities and Investments Commission and the Australian Securities Exchange.

Robertson’s target was a company run by a Tasmanian geologist named Nigel Ferguson. For three years, Robertson had tracked AVZ Minerals as it raised and spent $100 million for what Ferguson promised would be one of the world’s biggest lithium mines.