One of the challenges we have, I think, in leadership in education is we've still got the idea that everybody has to be super, or the system can't work. As far as I can tell you're only going to have 10% of people in your top 10% - that's the way I learned maths, anyway. So essentially, you've got to have a system that works with a significant number of people who are not absolute stars, because you are never going to have enough of them. You have to figure out some way for relatively ordinary competent people to do the job well.