You know how sometimes when you're asked whether or not you've done something, it can be hard to be sure one way or the other?
'Have I ever been to Shropshire... Hmm, don't think so, but I might have been, maybe on a family holiday...'
'Have I ever eaten sashimi... possibly... is that the sliced salmon one, or the one that's wrapped in seaweed?'
And then, other times, you can be fairly certain.
Do you know what, I never have.