“There are no more than five people in the world who understand money,” the investor Hugh Hendry once quipped. After the Bank of England and UK Treasury fired the starting gun this week for a British central bank digital currency, let us hope some of them are available to provide input.

The nub of the issue is how a central bank digital currency can coexist with our financial system and add to it without damage. At stake is not just the type of token we use to pay for things but the structure of finance itself.

To navigate the risks, many central bankers are proposing to create a “Goldilocks CBDC”: Not so much in circulation that it causes a run on the banking system as individuals switch savings to CBDCs, but not so little that it is irrelevant.