I don't think ANYBODY arrives at LHR at 0430 in any kind of airplane. They frown on that unless an emergency if I recall. You could arrive before 0600,but lost points or paid money to somebody so you tried to delay arrival.
On the 727, the speed brake on that airplane was probably the most effective on any airplane that I know of. It worked and the thing slowed. On the 727 you could only use speed brake with no flaps and the intial (was it 1 or 2?) was made as the speed brake was being retracted and you usually got a horn for 1-3 seconds.
JIMi