...get a quintessentially English prime minister from a priviledged background to issue an ultimatum to an autonomous small nation with a fear of said quintessentially English background. Then couch it in legal and constitutional terms that allows the populist (and popular) government to reject it in layman's terms that make their opponents appear to be arrogant and out of touch.
No doubt the champagne has been flowing in SNP headquarters today. Given the utter uselessness of the non-SNP parties in dealing with the SNP government in Edinburgh I'm not sure the timing or question of an independence referendum matters. Salmond will win it - whatever the question, whenever it is held.