It is well known that, at the close of the spring of 1687, the Dutch emissary, Everard Van Dyckvelt, having completed a brief, special mission from the court of William, Prince of Orange, Stadholder of the United Provinces, to the court of James II, the father of William's consort Mary, heiress-presumptive to the English throne, returned to his master at the Hague; and the high significance attaching to the return of the ambassador from a mission which, from a purely diplomatic point of view, had been quite unnecessarily undertaken, and which has rightly been called an embassy “not to the government but to the opposition”, has always been plain to students of Anglo-Dutch diplomacy of the months just preceding the Revolution of 1688. Indeed Mazure, the French historian of our Revolution, has declared with force and simplicity: “Le retour de Dyckvelt décida la fortune de Jacques II en fixant les résolutions du prince d'Orange”. Broadly, the statement is true. It was immediately after this embassy that the opposed policies of London and the Hague hardened into an irreconcileable opposition. The conclusion of the embassy is therefore that appropriate place at which, for the purpose of such a work as the present, to attempt to capture the aims and to gauge the character of the baffled diplomacy which, in so short a space, was to provide for Europe the spectacle of a prince intervening by force in the domestic concerns of his father-in-law, prosecuting a design quite indistinguishable from an overt act of war.