[Stooky Bill]

That is a very good question. They definately had a commercial data service, and I have seen a video of a text-based service on their boxes for some purpose.

The boxes had an on-screen now and next function, which of course was quite advanced for its time.

It is a good question, apparently DMAC had the facility for carrying teletext as a data burst alongside the audio. Presumably it couldn't be carried in the normal way, like on modern digital broadcasting standards where it has to be carried seperately. Seems other MAC broadcasters used the data burst for multi language subtitles

I'd have thought BSB used it for subtitles too, but according to this article they didn't include teletext decoders in their recievers:

www.newscientist.com