On the face of it, Frobisher’s first expedition was a disaster. One of his three small ships was lost in a storm and a second was abandoned. Five of his 35 crewmen were captured by Inuit, and he never found the passage.

But before returning home, his crew grabbed a quantity of “black earth”, believing it to be gold ore. Back in London, some experts were inclined to dismiss these samples as worthless. But Elizabethan metallurgy was an imprecise art, and when two prestigious German assayists announced that the earth was indeed rich in gold, a major new expedition was planned.

Egged on by her chief adviser, Lord Burghley, Elizabeth herself invested heavily in the enterprise, whereupon droves of courtiers followed suit. And in the spring of 1577, Frobisher again set sail for Arctic waters, this time with 120 men.

With the Northwest Passage now forgotten, they dug 200 tons of rock from several mines around Baffin Island and shipped it home. When this failed to produce much precious metal, the scheme’s backers blamed the poor processing facilities at Tower Hill. Whereupon the queen ordered a huge smelting works to be built down river at Dartford before sending Frobisher back for more.

The third voyage was a grand affair, involving 400 men in 35 ships. More than 1,000 tons of “black earth” were mined and shipped to Dartford. But even the new furnaces failed to extract much gold from it, and recent analysis of surviving samples explains why. The Elizabethan assayists, guided more by hope than science, had been thousands of times out in their analysis, and much of the “ore” contained less gold than an average piece of rock. But although Frobisher the Arctic explorer now found himself in somewhat hotter water, he survived the ensuing rumpus, only to be killed some years later leading an assault on a Spanish fortress.