When Charles Ponzi was arrested 105 years ago he had just raised as much as $20mn in seven months. Thousands of Americans had fallen for his scam investment scheme that promised to double their money in 90 days.

Depending on whether you are a signed-up crypto bro or not, bitcoin is either a brilliant innovation to move the world away from corruptible fiat currencies or a vast confidence trick. The advent of bitcoin treasury companies that raise debt and equity merely to buy bitcoin is, by extension, either genius financial engineering, or something akin to a Ponzi scheme upon a Ponzi scheme.

Such shorthand may be clumsy — crypto does not explicitly rely on new investors to remunerate existing ones as Ponzi did; and fraud, though sometimes connected with crypto, is not inherent to it. But there are still alarming similarities, most obviously the mood of cultish exuberance. Over the past year, bitcoin is up more than 80 per cent, four times the gain of the trendily tech-heavy Nasdaq index; who knows — it might manage 100 per cent in 90 days at some point.