Conversation so far:
How was Alexander Litvinenko poisoned?
Alexander Litvinenko's illness was later attributed to poisoning with radionuclide polonium-210 after the Health Protection Agency found significant amounts of the rare and highly toxic element in his body.
who poisoned Alexander Litvinenko?
Alexander Litvinenko met with two former agents early on the day he fell ill – Dmitry Kovtun and Andrei Lugovoy.
why was Alexander Litvinenko poisoned?
Expert on Russia Paul Joyal suggested that A message has been communicated to anyone who wants to speak out against the Kremlin.

Question: when was he poisoned?
Self-contained rewrite: when was Alexander Litvinenko poisoned?