The BBC World Service's station identification, uttered almost every hour on the hour, just before their short piece of theme music, "Lillibullero". Then come the 6 time signal beeps, followed by the words, "____ hours Greenwich Mean Time. BBC World Service." Very comforting to hear when you're far from home. Probably has been in use for decades, even before World War II, and perhaps derives from "This is London calling" (2LO's station identification in the 1920s).