I had somehow missed the reply to BrowserUk when I posted. I did write I have a feeling I'm missing the complexity here. And it did occur to me that Ovid was unlikely to have overlooked any simple solutions.

After seeing the reply to BrowserUk I considered updating my original. But I could think of nothing actually useful to add. So instead everybody gets your entirely accurate but somewhat snotty reply, and my waste-of-space defensive rebuttal. Luckily we are all professional enough not to take offense ;)