Nah gammon - A sneaky way to say you're lying, like you're hiding somethi

A sneaky way to say you're lying, like you're hiding something and you're not even trying to be clever.

Nah gammon, I didn’t eat the last slice of pizza. (He did.)

Nah gammon, I’m not dating my teacher. (He is.)

Nah gammon, I didn’t fail the test. (He did.)