B747-200 flight from DEL to LHR after 5 nights in Delhi. Crew on the flight deck preparing for push back. Ground engineer says "The Upper Deck toilet is out of action but the MEL says that you can go." Captain "That may be so but the Flight Engineer says that we cannot". "Why not?" says the ground engineer, "There is a toilet at the bottom of the stairs". "That is too far for the Flight Engineer" replies the Captain. The ground engineer was very wise and the upper deck toilet was fixed without question. I have to say that the only time that I ever had 'Delhi Belly' was as a result of eating the crew food onboard on a return leg to LHR.