Dear Mary: how do I politely ditch my hairdresser?

Q. I have just returned from a holiday where I was the guest of someone extremely rich. She was emphatic that everything would be covered and I must not even think of bringing a present. However, after one lunch in a restaurant, I felt driven to make a gesture and quietly asked the waiter for the bill. The sum involved was the equivalent of two months’ rent for me, but worse, no one noticed I had paid.  When the time came, everyone just got up to leave and I realised our host has an account with the restaurant, so she would not have noticed either. How, without being vulgar, can I let her know the financial sacrifice I made in a sincere, if misguided, attempt to show my appreciation?

– Name and address withheld

A. In your thank-you letter, briefly mention that you very naughtily disobeyed her diktat and paid for lunch at this restaurant.