In light of the recent Times 'best' schools guide, and, in particular, their list of 'top' 150 prep schools, it would be interesting to know whether it's a list out of potential, say, 300 or 200 or 150? (I have no idea, so just pulling numbers out of the air!) I'm aware of some of the wider criticisms of league tables in general and the Times ones in particular, but, putting that aside for a moment, how big a population are we talking about?