The following is a true story:
My friends and I were enjoying the atmosphere (and food) at an authentic English pub in town. We all ordered tea, and the barmaid brought us all our preferred variety. She passed by each of us and asked, “Would you like milk or lemon?” One of my friends simply said “Yes” and quickly poured a bit of milk and squeezed a lemon wedge into his cup. He passed the milk back to the young lady who smiled and said, “I’ll be right back with another cup for you, sir.”
My friend was confused at first, but upon her return he was happy to have a fresh cup. What had happened to necessitate a new cup of tea?
Answer
My friend was unaware that you never add milk and lemon to your tea as the citric acid in the lemon will cause the proteins in the milk to curdle, making for an unpleasant cup of tea indeed. The young lady had seen this happen before and moved quickly to remedy the problem. Afterwards, she only teased him a little about it.