The 75th anniversary of the Katyn massacre, in which more than 20,000 Polish prisoners were executed by the Soviet Union, will be marked this weekend in west London.
Radosław Sikorski, leader of the Polish lower house, will also join Christian and Jewish leaders for the ceremony, which up to 200 people are expected to attend.
The day of reflection will begin at midday, with a service at the Roman Catholic Church of St Andrew Bobola, in Leysfield Road, Shepherd's Bush.
A commemorative ceremony, organised by the Polish Ex-Combatants' Association, will then take place at 2pm at the cemetery in Gunnersbury Avenue, just south of Gunnersbury Park, where a Katyn memorial has stood since 1976.
A total of 22,000 Polish captives are estimated to have been shot by the Soviet Union's secret police on Stalin's orders during April and May 1940.
The massacre takes its name from the forest in modern day Russia where a mass grave containing many of those killed was discovered in 1943.