I'm sure I've done LHR-NCL through Gate 4 at T5 a few times. Is that the one where you go downstairs and there and a, b, and c exit from which buses take you to the aircraft?
If so, it's quite a confusing gate as there's seating before you go downstairs and many passengers aren't sure of what to do - whether to remain seated upstairs or go downstairs where there are just a handful of seats.