From what I can tell, a "king hit" is the Australian equivalent of what an American might call a "haymaker," one of those big old punches where you wheel back before you swing, and fall on your face if you miss. Getting clocked by one of those and being able to just pop up and run away speaks pretty will of Robbie McEwens toughness (not that it needed to be spoken for).
Can any of you Aussies out there back me up on this one?