Originally Posted by
ffay005
The passage from the departure hall to arrivals (at T3) is opposite gate 23. I will add this to the initial post. Basically you follow signs to gate 23 and just before reaching the gate on your left, there is a doorway on the right leading to airline desks and arrivals.
Took a pic during last visit. But there are reports on BA board that it is no longer possible to enter "wrong" terminal through transit path at LHR just for lounge hopping purposes.