Anne McElvoy discusses Katyn, the latest film by Andrzej Wajda, which depicts one of the most controversial massacres of the Second World War - the murder of thousands of Polish soldiers by the Soviet Army in Katyn forest in 1940. The slaughter has been a source of tension between Poland and Russia right up to the present day - even though President Gorbachev confirmed Soviet responsibility in 1990 - and the film has elicited mixed responses as to whether it offers an even-handed account of events. Wajda is one of Poland's most famous directors and his own father was killed in the Katyn forest.