My rusty French is a damn sight better than my Spanish, I once managed to book a table in a restaurant in Andalucia for forty people; they were a bit nonplussed when just four of us turned up!
Not that long ago I was in the south of France and got asked to translate for an English priest who was trying to organise mass in an abbey. My French, whilst faitly good, is a bit rusty having not used it for a couple of years. We had a discussion about the history of the abbey and the cross that was on the wall was supposedly donated by the Black prince because he used to take mass at that abbey. When trying to explain to the curator of the church who the black prince was I accidentally told him that he was the only prince of Wales to never become queen of England.
He laughed so hard he had to leave the room and I didn't realise what I had said wrong. It was only afterwards that I realised and had to apologise to the priest who thought I was making fun of him.