An 89-year-old film, which could take cinemagoers a marathon seven hours to watch, is returning to the big screen.

The new digitally-restored version of Abel Gance’s Napoleon comes at the end of a 50-year project involving the British Film Institute National Archive.

Running at some five-and-a-half hours on screen, the 1927 film demands a huge investment of resources – from projectionists, musicians, conductor and audiences, and in a live performance with intervals the experience adds up to more than eight hours from start to finish.

The film features full-scale historical recreations of episodes from the personal and political life of Napoleon, from the French Revolution to the arrival of French troops in Italy marking the beginning of the first Italian campaign of 1796.

From autumn this year, audiences will be able to experience this cinematic masterpiece with Carl Davis’s score when the film goes on theatrical release in UK cinemas.

The latest digital restoration of Napoleon will have its premiere screening with a live performance by the Philharmonia Orchestra of Davis’s score in early November at the Royal Festival Hall.

It has been entirely regraded and received extensive digital clean-up throughout, all of which offers significant improvements in overall picture quality.

It is the most complete version of the film available compiled by archivist and historian Kevin Brownlow, who spent more than 50 years tracking down surviving prints from archives around the world since he first saw a 9.5mm version as a schoolboy in 1954.

Heather Stewart, creative director at the BFI, said: “Napoleon is a landmark in the history of cinema and we are grateful to all of the great talents who have helped us along the way but especially, of course, Kevin Brownlow for his indefatigable championing of the film and Carl Davis for his amazing score.”