Sometimes the old ways of espionage are the best

From the mid-1960s until 2008 anyone tuning a radio to shortwave frequencies between 5.422 and 16.084 mhz would periodically hear a jaunty flute playing a few bars of an English folk song. Then, in a clipped English accent, a female voice would read out numbers: “Zero, two, five, eight…” The transmissions were thought to be coded messages from mi6. The “Lincolnshire Poacher”, named after the jaunty tune, was one of many “number stations” used by spy agencies to communicate with agents in the field.