He tuts at being told not to drink (never going to happen) and assumes they're done.

But then Guppy picks up the scanner. He takes one look at it and something inside him twists; he shoots to his feet and without thinking, a single fist is raised in threat.

'I told you to keep it away from me. Try it an' you'll be findin' bits of your teeth on th' floor for the next week.'