From today, France is banning the use of cash for transactions worth more than €1,000, or slightly more than £700. On one level, that is about combating crime and terrorism. But on another, it is also part of a growing movement among academics and now governments to gradually ban the use of cash completely. It is inefficient, oils the underground economy, and makes it harder for central banks to manage the economy, or so runs the argument. Much like gold, it is a “barbarous relic”, as some publications loftily dismiss it. The trouble is, cash is also incredibly efficient. And it is a crucial part of a free society.