Neatly dressed in his suit, Hans Ferdinand Mayer was every inch the unassuming corporate executive. So, when he asked to borrow a typewriter from his hotel in Oslo, nobody could have guessed he would use it for one of the most extraordinary intelligence leaks in history.

Mayer's gloved fingers punched out the details of Nazi Germany's most sensitive military operations and, when he had finished, he immediately dispatched his documents to the British — who did nothing.

Why did the British ignore Mayer? Did they fail to pick out a crucial signal amid the noise of detail — or was something else going on?

This episode of Cautionary Tales is based, with permission, on Tom Whipple’s book The Battle of the Beams, which is available from all good booksellers.

For a full list of sources, see the show notes at timharford.com.

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Cautionary Tales will be LIVE on stage in London this May. Tickets are on sale now: https://www.tegeurope.com/events/cautionary-tales/

Sam Israel had a problem. The investors in his hedge fund, Bayou Capital, were expecting spectacular returns. Sam himself had spent years proclaiming the fund's brilliant results. But in reality, Sam had been marking his own homework, publishing fraudulent accounts and using these to lure in new investors.

What to do? Well, the logical thing of course: wait around for an extraordinary profitable streak, and in the meantime keep up the ruse...

This episode of Cautionary Tales was recorded live at the Bristol Festival of Economics and studies three incredible investment scams. How do pyramid and ponzi schemes snowball out of control, flattening victim and fraudster alike?

For a full list of sources, see the show notes at timharford.com.

See omnystudio.com/listener for privacy information.

Bonus: When Spanish conquistadors arrived in Peru in 1526, it was the beginning of the end for the Inca. Their bloody pursuit of gold, fame and fortune was rife with treachery and deceit. Within a few short years, the once-thriving Inca empire had been decimated.

Tim Harford is joined by Dan Snow for a special crossover episode of Cautionary Tales and Dan Snow's History Hit. Tim and Dan first recap the spectacular defeat of the French knights at the Battle of Crécy in 1346, and then draw surprising parallels with the fall of the Inca Empire two centuries later.

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