Originally Posted by
RichardInSF
If that bus gets stranded in a long traffic tailback on the M25, even the "theoretical" 2:30 would go out the window. I wonder if the fastest (not cheapest, not easiest) way during possible traffic times is Gatwick Express-tube-Heathrow Express. Seems like that would always come in at less than 90 minutes. Or maybe taxi from Victoria to Paddington.
I find train-tube-train faster than the M25 except under ideal conditions on that roadway. I hear the M25 has ideal conditions some Sunday mornings from 3 to 4 am, but I've never seen them. Delays are the norm.
To answer the OP's question: half an hour to get out of LGW, 1:45 for the three-step transfer ... I'd say a 4-hour MCT would leave some wiggle room, but I wouldn't want to see anything less than 3:30. That would be too short if anything goes even a bit pear-shaped.