I can't see how it can be LHR. Remember, you have at least half a dozen US carriers that aren't allowed to fly there and must go to LGW instead, as well as many African carriers who can only get slots at LGW. Also, carriers like Garuda etc.
If you combined LHR and LGW together, that would definitely be number 1, but because of slot restrictions/Bermuda I can't see how it could be LHR.
I used to think the brain is the most fascinating part of my body. But, hey, who is telling me that?