Hoping someone can jog my memory about a scene from the books that's played out in 3e3.

The fight at the end there between Cauthon and the princelings.

In the books, I remember there was someone there that either was cautioning the prince beforehand (or after?) about how dangerous a simple quarterstaff is in the right hands.

Show didn't do that and I'm not questioning that change, rather I am just trying to remember who it was said that

Was it one of the brothers, and the other fought him alone? Or was there someone else there more experienced? Can't remember the scene properly after so long.