I was on a VS flight MIA-LHR many years ago. Back when the upper deck of the 744 was half Y+ and half J, as soon as the the upper deck looked reasonably full, an older guy got up from the row behind us, casually walked forward into J and plonked himself down in one of the Upper Class suites. He lasted about twenty second before one of the cabin crew (who had clearly watched him from the galley at the rear) stormed up the aisle and escorted him back to his assigned seat.