It’s worth thinking about that promise to ‘pay the bearer on demand the sum of ten pounds’. When we parse it, it’s not clear what it means. Ten pounds of what? We’ve already got ten pounds. That’s exactly what we’re holding in our hand. It doesn’t mean, pay the bearer on demand ten pounds’ worth of gold: the link between currency and gold was ended in 1971, and anyway, Gordon Brown sold off the Bank of England’s gold reserves in the 1990s. The fact is, there’s no answer to the question, ten pounds of what?