"The longest running daily cartoon strip by a single author is "Bristow" by Frank Dickens (UK) which has been in continuous publication since first published in the Aberdeen Press & Journal on 18th September 1961."
This looks to be, in part, an older English language documentary, with Mr. Dickens (whose 81st birthday is tomorrow) talking about the creation of his comic strip. The narration and the comics are in Italian.
Here is a longer, different version from the 1960s:
This is, so the YouTube info tells me (translated from the Italian):
Excerpt from the series SMOKE INK on the masters of comics. Frank Dickens tells the story of his most famous character: Bristow.