Throw a Brit in the mix who starts effing and blinding making it quite clear that they are going to get a kicking momentarily...
In the US it is used, amongst the press at least, to mean "in a moment" as opposed to "for a moment."
I recall watching a news item about a presidential visit somewhere or other, which showed footage of the pax door of Airforce One on the apron and the assembled journos were waiting for the cheese to pitch.
The telly reporter tried to fill in the time by repeatedly saying, "and this is the door where the president will appear momentarily."
We had visions of the besuited main man hopping into the doorway, smiling, then jumping backwards out of shot.