He also put something of a pin in Nicola Sturgeon's ambitions, saying: "The negotiations will be conducted with the United Kingdom, not with a part of the United Kingdom."
For those that recall IndyRef, there was some coverage of the fact that there are other countries in Europe that face a unity challenge. Spain and the Basque region being the most obvious.
Given the map of Europe has been redrawn many times since 1914, it's entirely possible there are other simmering bids for autonomy just looking for a lead.
Much as the EU might like to treat Scotland as separate from England, it knows the dangers of playing to minor characters too well. I know Italys unity is less than perfect, and there is a strong sentiment they should dump the south.