Years before David Cameron, John Major proposed to the Scottish nationalists that if they wished to be independent, then a referendum, binding in its consequences, could be held on the matter; but that in no case would he enter into a dynamic of growing concessions that would lead to independence anyway.
Blair's reform brought, in 1999, a Scottish parliament that elects a government with fairly ample powers. In the 2007 elections, the Scottish National Party (SNP), whose program included a promise to call a referendum on independence, received the most votes. It formed a minority government with the Greens, but had to back down on the referendum when a majority of the Chamber refused to put it on the agenda.
The result suggested that the upsurge of separatism boasted by some enthusiasts should be taken with a few grains of salt. Some polls had gone so far as to put separatist opinion near to 50 percent. But when the question was posed offering various formulas (centralism, autonomy, full independence), the last of these dropped by half.
The nationalist leader Alex Salmond's response was to reformulate his proposal: though considering independence the best option, he admitted there were others and proposed discussion on various alternatives, in terms of cost-benefit. After that, a referendum would be called, offering the citizens three possibilities: maintenance of the status quo, increase of autonomous powers or independence.
It so happened that in the next elections, in May 2011, the SNP obtained a clear majority, which in principle gave it a chance to call an independence referendum. But it has stuck to its triple-option formula, apparently in the hope that the vote will go to the intermediate one - stronger autonomy - the main novelty of which is that it will include an autonomous system of tax collection, similar to that in certain territories of Spain.
Michael Keating, author of Nations Against the State , which compares regional nationalisms in Catalonia, Quebec, Scotland and elsewhere, was one of the first academics to discern the emergence of separatist movements of primordially economic motivation. The most extreme version would be Umberto Bossi's North League (Liga Norte) in Italy. But for some time now, Catalan nationalism has been headed in a similar direction, as has the Scottish kind.
Beginning in the late 1990s, Keating often traveled to the Basque Country, and in 2003 published a (favorable) study on Ibarretxe's sovereignty plans. He took particular interest in the political treatment of tax collection: regional collection of all taxes, and a quota to be paid to the central state's revenue ministry to defray the costs of the remaining competencies of the state - army, foreign affairs, royal family, frontiers, etc.
This formula has obvious attractions for the Scottish nationalists, as it offers the advantages of independence without its burdens. Salmond now talks of maintaining the link with London in matters such as currency, defense, monarchy, etc., and of independent power to manage all the tax income generated in Scotland, including that proceeding from North Sea oil. But this is a risky system: favorable if there is growth, but barren of alternatives if there isn't. At present the Scottish receive more funds per capita than the English.
Salmond's proposal amounts to further concessions: just what John Major refused. Now Cameron, in demanding that the referendum be binding, and that it pose the question of independence, yes or no, is trying to forestall a frivolous pro-independence vote, and to avoid the trap that awaits every process of decentralization: more autonomy, culminating in a demand for independence.
In Spain we know a lot about these matters: for example, about complaints that the central state is breaking the agreed constitutional rules whenever it frustrates regional aspirations such as that of limiting what the region must pay for the sake of state-wide solidarity.