This is a Belgian TV documentary on Tintin based on Gérard Valet's interview with Hergé. It has some remarkable footage of Herge's reunion with his old friend Chang (from The Blue Lotus and Tintin in Tibet) at the airport in Brussels.
Although it was originally in French, here is a great chance to see it with English narration (and English subtitles when necessary) from Australian television.
Although this documentary originally dates from 1976, I think it was redone a bit (added footage, etc.) in the early 1990's - if anyone knows the story there, please explain in the comments.
The quality is not pristine, but all things considered it is very watchable considering it's age and rarity.