When visiting the cafeteria, it is considered polite to pay for the things one has ordered before leaving.

bangs head slowly and rhythmically against desk

My apologies to the splendid people with whom I had lunch today for wandering out absent-mindedly without coughing up the four quid owed to the establishment for my all-day breakfast.

In the event that any of you felt obliged to settle the bill in my absence, I hereby promise to redeem the debt with alacrity next time we meet…

Update: The Big Other is propitiated: I have paid for my breakfast.