Channel 4 Teletext c.1995
This is an 11-minute video showing a sequence of "pages from Teletext" broadcast on Channel 4 which I found at the end of an old videotape in 2017. It is most likely to be from around May 1995 according to analysis of the TV listings shown.
Interestingly, the video shows animated Teletext sequences; it's unclear if these would have been available when viewing Teletext at the time or whether the animated sequences were specially made for broadcast as programme material.
The videotape format is long-play VHS, and unfortunately no Teletext signal could be detected either from a Teletext TV set or an Acorn Teletext adapter.