Many thanks for the insight, and information. Especially "controllerzhu" and the word from the horses mouth.
With regard to the
heavies are issued "do not exceed 280kts" - I believe because we were told some heavies don't perform well at 250kts, or some such thing.
Typically airborne from LAX, for LHR a -400 will not get clean until about 270kts. So in the climb at 250kts you are climbing with a shed load of flap out. 280kts lets us get clean, and efficient.