An independent Scotland will not keep the pound. That’s despite this being the express wish of the Scottish government, which is campaigning for independence in September’s referendum. The reason is that it’s hard to see the rest of the UK agreeing to such a deal – except on terms that would affront Scotland’s amour propre.

One can understand why Edinburgh is keen not to change its monetary arrangements. If Scotland had its own free-floating currency, it would be less economically integrated with the rest of the UK. Given that 60 percent of its exports and 70 percent of its imports are with the rest of the UK, such a separation would hit hard.

A separate currency would also cause trouble for the outsized Scottish banking sector. Banking assets are more than 12 times GDP – nearly double the ratio for Iceland, Ireland and Cyprus before their banking industries blew up. The Scottish people might also worry that a Scottish currency could fall in value, devaluing their savings.

Joining the euro might not be any better. Like a separate currency, the euro would complicate Scottish trade with the UK, and the euro zone might be unhappy with Scotland’s relatively gigantic banks. Added to that, the euro has suffered years of terrible publicity, so promising to join it wouldn’t be a vote-winner.

No wonder Alex Salmond, Scotland’s first minister, is pledging a currency union with the rest of the UK. The snag is that such an arrangement would be virtually impossible to negotiate. Mark Carney, the Bank of England’s governor, gave some of the background thinking in a speech in Edinburgh last week.