But he quite understood that Prussia must have some recompense for the help it had given.

What he had to fear was that, if he entered into any separate and secret engagements with Prussia, he would thereby lose the support he enjoyed in the rest of Germany, and that then Bismarck would find some excuse not to carry out his promises, so that at the end he would be left entirely without support.

We know that his suspicions were unfounded, for Bismarck was not the man in this way to desert anyone who had entered into an agreement with him, but Augustenburg could not know this and had every reason for distrusting Bismarck, who was his avowed enemy.
On the 30th of May, the Prince, with many misgivings, came to Berlin.
The evening of the next day he had a long interview with Bismarck; it began about nine o'clock and lasted till after midnight.

There is no doubt that this interview was decisive against his chances.

From that time Bismarck was determined that under no circumstances should he succeed, and we shall see that when Bismarck wished for anything he usually attained it.