It is 13:03 on a Tuesday in a cramped room with some fairly advanced radio equipment. What is suddenly heard on a shortwave receiving station is a 10-minute message in Morse code.
There is a small community of aficionados who believe messages like this are a throwback to the era of Cold War espionage. They are the mysterious "numbers stations".
At the apex of the Cold War, radio lovers across the globe started to notice bizarre broadcasts on the airwaves. Starting with a weird melody or the sound of several beeps, these transmissions might be followed by the unnerving sound of a strange woman's voice counting in German or the creepy voice of a child reciting letters in English.
Encountering these shortwave radio messages, many radio hams concluded that they were being used to send coded messages across extremely long distances. Coming across one of them was a curious experience. Radio enthusiasts gave them colourful names like the "Nancy Adam Susan", "The Lincolnshire Poacher," "The Swedish Rhapsody" or "The Gong Station."
The Lincolnshire Poacher was so named because of two bars from an English folk song of that name being used as an "interval signal".
Times have changed and technology has evolved, but there's evidence that this old-fashioned seeming method of communication might still be used. Shortwave numbers stations might seem low-tech but they probably remain the best option for transmitting information to agents in the field, some espionage experts suggest.
"Nobody has found a more convenient and expedient way of communicating with an agent," says Rupert Allason, an author specialising in espionage issues and writing under the pen name Nigel West.