Tom, who drinks IPA

A regular at the P. is Tom, who drinks IPA. I know this because he once said to me "I'm Tom, and I drink IPA."
Someone once left about a fifth of a pint on the bar. I saw Tom sidle up to it and regard the glass for a moment. He put his own pint down next to it, picked up the forgotten drink, looked from side to side, downed it, and put the now empty glass back on the bar. He then slipped away with his own beer. I was stunned.