CITY Screen, York is to show the premiere of the Edward Snowden documentary, Citizenfour, tomorrow at 8pm, followed by a panel discussion beamed live from the 58th London Film Festival via satellite.

In January 2013, filmmaker Laura Poitras was several years into the making of a documentary about abuses of national security in post-9/11 America when she started receiving encrypted email from someone identifying himself as “citizen four”, who was ready to blow the whistle on the covert surveillance programmes run by the NSA and other intelligence agencies.

In June 2013, Poitras and reporter Glenn Greenwald flew to Hong Kong for the first of many meetings with the man who turned out to be Edward Snowden. She brought her camera with her.

"The film that resulted from this series of tense encounters is absolutely unique in the history of cinema: a 100 per cent real-life thriller unfolding minute by minute before our eyes," says City Screen marketing manager Dave Taylor.

Tickets for Citizenfour and the satellite question-and-answer session cost £9, concessions £8, members £7, on 0871 902 5726 or at picturehouses.co.uk/york