Alexander Litvinenko, a former officer of Russia’s security services who later became a critic of the Kremlin, died in London on 23 November 2006 after being poisoned with the radioactive isotope polonium‑210.
A UK public inquiry (reported in 2016) concluded that Litvinenko was poisoned by two Russian nationals and found that the operation was “probably” approved at senior levels of the Russian state. The case became a benchmark example of a state-linked targeted killing carried out abroad using a rare and hazardous substance, raising major questions about accountability and deterrence in Europe.