The 'herbal' brew contains a number of naturally-derived ingredients, including Guarana, Maca Root and Tongkat Ali, a Malaysian plant said to have Viagra-like properties.

There was even an ABC news documentary about it, which is available on the Stiff Bull website.

Chris Keelan, the guide, said:

"Will it work as quickly? No. But it also won't cause potential heart attacks, stroke; potential deafness or blindness."

Seems safe, and surely it's been approved by the relevant food regulatory bodies?

Well… not exactly.

The Stiff Bull website states:

"Actually, no dietary supplement is 'approved' by the FDA. They are, however, stringently regulated and must comply with the provisions of the Dietary Supplement Health and Education Act of 1994 as regulated by the FDA."