Almost everyone on this thread has decided the poor chap fainted due to lack of food or water. I have known a pilot faint due to having his collar buttoned up and when he turned his head quickly it just slightly restricted his throat. Once his tight top button was unfastened he was fine. The question in the above case is will the CAA ground the guy for a long time and make him undergo a load of tests and be reluctant to give his medical back.