The reason is that Syme has on several occasions threatened to molest the King and members of the Royal Family, and has written letters to His Majesty threatening annoyance. A speech containing threats against His Majesty is the ground for the recent proceedings against him.
It is a fact that he is very dangerous when he is out, and the
alternative is between letting him die in prison of hunger-striking or letting him out. He is a very dangerous man and very difficult to deal with.