Originally Posted by
bealine
Passengers arriving from a UK Domestic service are not required to pass through additional security at Heathrow.
Passengers arriving from anywhere else in the world connecting to a UK Domestic service are all required to pass through security at LHR.
So a separate connecting bus for UK Domestic passengers is only useful in one direction.
Useful nonetheless for us domestic transfers. Surely not dumping more already screened to UK standards passengers through security again is better for everyone,
including those who aren't transferring as the queues will be smaller and therefore get through T3 (or any other terminals) security channels.
As
Globaliser said, the bus then can be used for bringing passengers back to T5 or any other terminals.