After having read twice the scene in A Clash Of Kings, where Tyrion Lannister sends:
Lord Janos Slynt to join the Night's watch.
I'm a little confused. I understand somewhat why Tyrion does it, I'm just a little confused as to how he managed to pull it off without being cut short by his sister.
Cersei wanted Slynt in command of the City watch, did he really spirit Slynt away without her noticing? Wouldn't Cersei have taken measures to get Slynt back?
I'm discussing the books here, although having rewatched the scene in the TV show where it happened, they seem similar enough as for it not to matter.