Quotes of the Day

Polonium-210 has a half-life of 138 days. Yet 30 weeks after the substance was administered to Russian dissident Alexander Litvinenko, its potency seems undiminished, contaminating relations between two former imperial powers and pitting the demands of justice against the exigencies of realpolitik. London's request to Moscow on Tuesday to extradite Andrei Lugovoi as chief suspect in Litvinenko's murder drew a response that's increasingly familiar to Kremlin watchers: an abrupt no. There were some obvious reasons for Russian intransigence. The case is a skein of disputed plots and subplots. Lugovoi and one companion — or two, according to some versions — met Litvinenko at a London hotel on Nov. 1. Litvinenko died 22 days later from the invisible toxin apparently swallowed at that meeting. British investigators have tried to unpick the events, linking Lugovoi to a trail of particles shed by the polonium. Lugovoi denies blame, while Russia says its constitution prevents it from handing over a citizen to a foreign power.

Moscow has helpfully suggested that its own authorities investigate the crime — an offer met with skepticism in Britain, given that Litvinenko, on his deathbed, blamed the Kremlin itself for his fate. His accusation has fed fears that Russia increasingly operates by its own rules. That's a view promulgated by billionaire Boris Berezovsky, an opponent of President Vladimir Putin. Some Russians believe in another conspiracy: that Berezovsky, who has claimed asylum in Britain since 2000, engineered Litvinenko's murder to embarrass Putin. Berezovsky strongly rejects these claims and has donated $1 million to a foundation set up by Litvinenko's widow to seek justice for her husband. But justice — and a clear outcome — could further strain U.K.-Russian relations. Britain and its European allies need Russian support to resolve international conflicts and combat climate change; and they're uncomfortably aware that the country supplies much of Europe's natural gas and oil. So, while politicians trade hard words, their instinct for appeasement is strong. The mystery gripping Western diplomats is not who murdered Litvinenko, but how to contain the political poison that his killers have unleashed.

• CATHERINE MAYER
• Britain wants Litvinenko suspect Lugovoi. Forget it, says Moscow