She flashed them in Istanbul, she pointed them at Paris, but she kept them in their holsters when she visited London. What's that about? To be fair, the bra she's wearing is practically gossamer, so even when she's not flashing a crowd, she's flashing a crowd.
Perhaps London simply wasn't ready for her bare nipple, or maybe some concert organizer asked her not to. It sounds insane (who could possibly have the balls to tell Madonna not to show skin on stage?) but considering that someone recently pulled the plug on Bruce Springsteen and Paul McCartney when their show went past curfew, it wouldn't be all that surprising. Nipple politics: they're a trip.
Anyway, at least she flashed her thong to London!