Originally Posted by
lhrsfo
IIRC years ago they said that they would not build it until they got permission for the third runway.
I think that this is still the case although, more recently, HAL have talked about the need for modernisation ahead of the third runway. Essentially, they want to replace T3, but doing so means creating capacity elsewhere for airlines to move into. In the short term, this means maxing out T5, initially within the existing planning application. This is then followed by the extension of T2A and building of T2C.