Once upon a time I was walking with a friend around Amsterdam and a man walked up to me and asked me where something was (a nearby restaurant), I answered in English with directions and he thanked me, then a moment later this exchange happened:

- Wait! You can speak Netherlands?

- No. Sorry.

- But you can! I am speaking it!

- No you're not! You're speaking English!

He just blinked and walked off, probably assuming I was playing a trick, but my friend asked what that was all about, and had to convince me that she didn't understand anything he was saying, and wouldn't have said anything to me at all about it except that she heard me insist he was speaking English!

She asked me to try and remember what exactly I was hearing, and I realised I couldn't! I could only remember something like "do you know where [placename that sounded familiar] is?" and maybe that there was a heavy accent, but not exactly how it sounded.

Every now and then I think of this and I wonder if I actually understand English at all, or if I'm just so used to saying that I understand it (in response to something that sounds something like a question) that I started to believe it.