Harold, the Last of the Saxon Kings Book XI: The Norman Schemer, And The Norwegian Sea-King by Edward Bulwer-lytton

Brief was the sojourn of Tostig at the court of Rouen; speedily made the contract between the grasping Duke and the revengeful traitor. All that had been promised to Harold, was now pledged to Tostig -- if the last would assist the Norman to the English throne.

At heart, however, Tostig was ill satisfied. His chance conversations with the principal barons, who seemed to look upon the conquest of England as the dream of a madman, showed him how doubtful it was that William could induce his Quens to a service, to which the tenure of their fiefs did not appear to compel them; and at all events, Tostig prognosticated delays, that little suited his fiery impatience. He accepted the offer of some two or three ships, which William put at his disposal, under pretence to reconnoitre the Northumbrian coasts, and there attempt a rising in his own favour. But his discontent was increased by the smallness of the aid afforded him; for William, ever suspicious, distrusted both his faith and his power. Tostig, with all his vices, was a poor dissimulator, and his sullen spirit betrayed itself when he took leave of his host.