He didn't specify if I could or not, but when I tried on the first night the flavour suggested it was useless to try. I however, have not been told about a knife.
If Zell tried to target Flink on the same night I did, then it makes sense that I stopped him and confirms my power. Also, if Zell is trying to lead people into thinking that holding a knife is nefarious, I would like to remind him of what alignment the majority holds.
If you confirm you are Langley, what say you to your character's relationship with the Queen?