I think you may have misunderstood the point I was trying to make with my posting, cavortingcheetah. It is the order of priorities as an airman to which I was attempting to allude to, in that your aircraft will still fly regardless of your theoretical knowledge of principles of flight however, you will not be sat inside the aircraft should your medical licence have expired!
An instructors ability to impart knowledge of relevance to a PPL holder whilst keeping his ego in check by refraining from trotting out streams of irrelevant technical information to confuse the student being another point which I aimed to make, therefore I apologise if you caught the wrong end of the stick.
VFE.