If someone brings you a pillow while you're sleeping, that person must be the Great Prince.
Marvin never imagined that his plans to form the Labour Party with the Fourth Prince would be resolved by the Great Prince in such a way!
And it all seemed so natural!
Arthur was also surprised by the Great Prince's determination, realizing that this situation could only mean that the Great Prince was under immense pressure, enough to make a blunder.
If Marvin and Arthur were sincerely joining him, then the offer to join the council was not a blunder but a brilliant move.
The key was whether Marvin and Arthur were double agents, who, on the surface, swore allegiance to the Great Prince but were actually infiltrating the core of his power, preparing to dissolve it from within.