Chess grandmaster Viktor Korchnoi, who defected from Russia to the West in 1976, has died in Switzerland aged 85.
Mr Korchnoi is regarded as the best player never to be World Champion.
He was a four-time Soviet Union champion and ranked number one in the world in 1965.
However, he left the USSR after being banned from playing internationally.
He played three matches against Soviet rival Anatoly Karpov, losing the 1974 final of the Candidates Tournament - which determines the challenger to play the world champion.
Mr Karpov became world champion in 1975 and Mr Korchnoi faced him in both the 1978 and 1981 World Championship finals, losing on both occasions.