ONE young man sitting in a forest used a laptop and a mobile phone to temporarily wipe more than $314 million off the value of Nathan Tinkler's Whitehaven Coal on Monday morning.

The Australian Securities and Investments Commission is now investigating the elaborate hoax, in which anti-coal campaigners issued a fake press release and impersonated a corporate affairs spokesman from ANZ Bank.

Hoaxer Jonathan Moylan. Credit:Kitty Hill

The hoax press release said ANZ had reversed a decision to provide a $1.2 billion loan to Whitehaven - of which embattled magnate Mr Tinkler is the main shareholder - sparking a sudden sharemarket sell-off when it was emailed to journalists at 11.44am. The company's price dropped about 8.8 per cent and Whitehaven was put into a trading halt. It resumed trading in the afternoon after news of the hoax spread, and shares closed at $3.50, just 2¢ lower than Friday's closing price.

Whitehaven recovered all but $20.38 million of the $314 million it had lost.