Reading a letter at the breakfast table, a wife suddenly looked suspiciously at her husband.
“Henry, I’ve just received a letter from my mother saying she isn’t accepting our invitation to come and stay, as we don’t appear to want her. What does she mean? I told you to write and say that she was to come at her own convenience. You did write, didn’t you?”
“Er, yes,” said the husband. “But I couldn’t spell ‘convenience’, so I made it ‘risk’.”