Director Detlef Siebert describes the painstaking process of restoring archive for I Was There: The Great War Interviews, scheduled to be shown on BBC Two, Friday, 14th March, 2014.
The greatest challenge was to find the film material for the selected pieces of dialogue. The Great War series was produced on 35mm but because 35mm reels allowed only four minutes of recording, the interviews were shot on 16mm, which allowed a longer recording time of ten minutes per reel – an essential requirement for in-depth interviews.
However, the costs of blowing up all the recorded 16mm footage to 35mm was prohibitive, so selected parts of the interviews were assembled in separate section reels for transfer to 35mm. As a result, each interview was spread over several reels.
Source: BBC Information & Archives
See Also: I Was There: The Great War Interviews (Detlef Siebert BBC Blogs)