The memoirs of political leaders are a literary genre without great prestige in both Catalonia and Spain in comparison, for example, to how they are treated in the United States or in France, to mention two very different countries. In part, because they rarely solve many of the enigmas that remain in the air, and the political leader concerned does not clarify any of the major questions of the moment.
However, we should be grateful to former Spanish prime minister Mariano Rajoy for shedding light on the negotiations that took place between the time of Catalan president Puigdemont's appearance in Parliament on October 10th, 2017, to declare that he was assuming the mandate of the people of Catalonia after the referendum on the first of that month, and the Parliament of Catalonia's declaration of independence on October 27th. Basically, because many people tried to intervene from positions very distant from the Catalan independence movement in an effort to convince Puigdemont that, if he stepped back, the Spanish government would not apply article 155 of the Spanish Constitution, instituting direct rule over Catalonia from Madrid.
There was toing-and-froing of both amateur mediators and significant politicians, such as Basque Country president Iñigo Urkullu who called on president Puigdemont to change his mind and call elections with the intention of avoiding 155. Puigdemont demanded guarantees... which never came. However, it has always been left hanging, because this is what the official narrative from Madrid demanded, that things would have been different if the Catalan leader had called elections instead of making a declaration of independence.
Rajoy destroys this theory in just a few lines, with an advance extract from his memoirs Una España mejor - A better Spain - in which he totally discards the proposition: "I saw no reason to suspend a decision that was not the result of a whim, but rather the consequence of weeks of study and of very solid legal and political arguments. Before reaching the point of applying that constitutional article, we had built up a great deal of justification for it and that did not disappear though Puigdemont's calling of elections; independence was still declared." The Catalan president's last actions in requesting written guarantees only provoked a reaction of "we're going round in circles again" from Rajoy.
And that was how Spain was incapable of sitting down to negotiate.