Which is madder, bitcoin at $41,500 — oops, make that $31,000 on Monday — or Tesla shares at $880 apiece? Don’t get me started on the crypto-mania in which the Financial Conduct Authority has warned gamblers ‘they should be prepared to lose all their money’. But Tesla, relatively speaking, is a real thing: a California-based carmaker which has expanded the frontiers of the electric vehicle market that’s going to become huge in the next decade and could soon make carbon–fuelled road transport extinct.