Born in Kolín near Prague on 4.11.1926. In 1938, at the age of eleven, went to England with his parents to escape the Nazis. His father at the age of 39 joined the Czechoslovak Army and with the artillery saw service in North Africa and Dunkerque. In the meantime, Jiří Theiner attended Leamington School. In 1945 the family returned to Prague and Jiří Theiner joined the English-language section of ČTK (Czechoslovak News Agency). Having refused to join the Communist Party and the Youth Union he was sacked after 1948 and sent to the Silesian coal-mines as part of the PTP (forced labour units).
After returning to Prague he worked as an editor at Artia and in 1962 went freelance as a translator working from home (during this time his translations included the poetry of Miroslav Holub which was published by Penguin in London).
Following the Soviet-led invasion in 1968 he left for England with his wife and two children. He worked for three years for publishing companies before finding his niche as the Assistant Editor of Index on Censorship under Michael Scammell. He became Director of Writers and Scholars International and Editor of Index on Censorship in 1982 and fulfilled these posts until his death on 15th July 1988.
Jiří Theiner was widowed soon after coming to Britain in 1971. He was remarried to Shirley Harris, with whom he lived until his death.
During the 1970´s and 1980´s Jiří Theiner promoted Czech literature and poetry abroad, and his commitment was paramount to freedom of expression throughout the world and publicising its persecution (above all in Czechoslovakia.) During this time his translations included works by Ivan Klíma, Ludvík Vaculík, Václav Havel and many others.