I've done the reverse in <45 minutes. As previous poster mentions, first off the plane, brisk pace, catch first bus transfer and stand close to exit, fast track, hand carry does not get pull for secondary security.
I had a return flight to the USA, my first flight was delayed making my 2.5hr layover to just 50 minutes. We landed @ LHR, but still had to wait almost 20 minutes for a gate assignment. We where last to board the plane. Something that has not been mentioned is that OW will have connection service indivuals upon arrivals to assist those with tight connections, or offer re booking. This helps on that you do not need to go to another area and re-confirm your details.