TfL are looking into this as apparently it had nothing to do with any members of staff, who fancied a quick break from normal announcements.
"It was definitely a couple doing it there and then," Laura O'Connor told the Evening Standard. "As the doors opened, I could hear these strange noises coming over the loudspeaker. It dawned on me what it was and I couldn't stop laughing. He was grunting loudly and she sounded like she was having a great time. The driver must have heard it, too, as the doors stayed open longer than usual."
A spokesperson for TfL said "The noises heard by passengers were not from within our station. We believe they were a result of some sort of interference with our public address system,"
John W who gave me the heads up (& title) on this story said:
"This reminds me of when (I think) Mark Thomas or some journo programem years ago managed to broadcast messages on a European train journey without hacking into the system or breaking any wires and managed to broadcast his disgust of the price or journey time or some political thing.
So it makes me wonder: How secure are these systems that are now being rolled out across the network under the hoardings of "We are improving your station" Answers on a postcard please!!!!!"