Clarification of Concours D'etat Rules Chapter 5 (5.2 b)
5.2 b States that the underbody will not be judged.
I have been lead to believe by some judges that this includes the wheel arches could I get a defined description of the above.
If it does, I find it hard to believe that a car can be judged with clean body work but dirty under the wheel arches particularly under the wheel arch lip which can hide a lot of road grime, I look forward to your reply.

Regards Harry Bluett 
To my understanding and in my experience, that is not correct, ie., it does not include the wheel arches.. The underbody refers to the under floor-pan of the car; the wheel arches surrounding the wheels should be looked at for all aspects of judging relative to D’Etat, ie., general condition and cleanliness.
Because it is D’Etat, there may be some aspects of the car’s body which may not be authentic, potentially including the wheel arches. If that was the case, then they would not be marked down, only potentially for cleanliness and general condition.
That is the main difference between D’Etat and D’Elegance; if the car was being judged in D’Elegance and the wheel arches were not correctly authentic, then they would be judged and marked down for incorrect authenticity, as well as, potentially, for general condition and cleanliness.
It is generally for that authenticity reason that people are wary of competing in Concour D’Elegance.. For me it is the reason that cars should be entered in D’Elegance; to help the owners improve their car progressively and find out where they have let themselves and their car down.
Regards ACJC