If your flying business class you'll get to go through the fast track, I would clear customs there instead of riding the buses between terminals. Then walk the underground to terminal 3 or vice versa 1 and stretch those legs and cobwebs out after a long flight. You'll get there faster (most times) and not be stuck in long lines and then have to clear customs over in terminal 1. I've done this many times and it sure beats a bus ride and long lines anyday.


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Cheers Scott