I would have to disagree with the tests being 90% natural aptitude and 10% how much revision you do. It may seem like this but they are something you can improve a lot on by practicing similar tests, especially under time pressure. I'd say you can improve your scores by 25-50% at least by putting a load of work in. I guess there will be a few 'sky gods' that are just naturals and don't need to revise, but the vast majority (myself included) benefit a lot from revision.