In November 2006, the world was shocked by the murder in London of former Russian intelligence officer, Alexander Litvinenko. We hear from his widow Marina about his life and agonising death, and get an analysis of the case from Luke Harding, author of "A Very Expensive Poison". Also in the programme, an astonishing assassination plot during El Salvador's Civil War, a huge oil spill in Spain, and the purpose-built city in Siberia which was home to the Soviet Union's best scientists.

(PHOTO: Alexander Litvinenko in a London hospital a couple of days before his death in November 2006. Credit Getty Images.)