The near future possibilities look more interesting every day.
And if it was indeed a smuggling operation gone bad, Russia would be one of the prime suspects. If so, the real question is...what were they up to???
"German police have told the Berliner Zeitung this week that they are looking into the possibility that radiation poisoning victim Alexander Litvinenko and his associate Dimitry Kovtun were involved in smuggling polonium out of Russia. According to RIA Novosti, one German police source told the Berliner Zeitung that the polonium 210 shipment that killed Litvinenko could have been valued at $25 million. German detectives have found traces of polonium in Dimitry Kovtun's apartment in Hamburg, and Russian investigators are treating him as a potential witness in the murder case."
http://www.russiablog.org/2006/12/german_police_suspect_polonium.php
PSS At this point, we must not rule out the possibility that Litvinenko was a phony defector/Russian agent who used his "dissident" status as a cover to operate in Great Britain