Just how much would all the high speed rail and road links to Rhoose cost?
Think of a number. Double it. Then double it again, a few times
To be a high enough speed line from Heathrow to make this viable, it's going to need to be a dedicated line - can you imagine what a train running TGV style would do to the dear old commuter trains chugging from Reading to Didcot if they used the existing line? How much for a new Severn Tunnel, or a lovely viaduct (high enough for the ships to pass)!?
I bet the cost would make a third AND fourth runway at Heathrow look like loose change...
TA