Originally Posted by
ajax
You can't walk to T1/2/3 (AKA 'Heathrow Central'). You can, however, take a free bus from many places around it. There is a zone (I can't remember the exact details but it says it on all of the bus-stop sign posts where this applies) within which bus drivers will take you to the Heathrow Central bus terminal for free.
I believe it's called the Heathrow Freeflow free fare zone.
You can see all the bus routes serving T2/T3, along with the stops that they make in the free zone, on
this map from TFL. (There are other buses that are free in the zone, for T4 and T5, that map just does the ones serving the central terminals)