Originally Posted by gmt4

At LHR there is security screening when changing between terminals. Inter-terminal transfers are separate from arrival customs and baggage claim. Terminals are all geographically separated and not connected airside. You follow the purple colored transfer signs and they led you to transfer busses, then on to the next terminal you need - 2,3,4,5. I suppose you could go all the way out through passport control and immigration then back around though the departures hall of the terminal you need but that's pointless to do.