Ahhhh ... (The meaning of the question finally clicks).
The whole Polonium thing worried me at first, but now I figure its the secretive world of spies and espionage just doing the same old things that they've been doing for fifty years. I remember from Spycatcher a story about the MI6's "Black Museum" which includes a tiny ball bearing used to kill a Russian defector in London in the sixties. It was loaded wih some sort of poison, and injected with a jab from an umbrella tip on a crowded train.
The only reason people even noticed this time is that it happened in London, and the story reached the press.