I spotted this on YouTube at the end of an original transmission of Millionaire, so I took a screengrab, not very good as it was originally presented in glorious mushyvision on YouTube but a download and local grab made it slightly more bearable:
Anyway I thought: That's a slightly unusual Teletext logo, with the "box" around the text bit, and do you know what, I can't find any other Teletext logo like it. I know it wouldn't look anything like that on the service itself if that was used because of, well, the blocks.
So I suppose the question is: I presume the yellow on blue text that was effectively their logo on the service and on the odd occasion where it was seen outside of Teletext (before they went down the all purple route) but when was that logo with the rounded box introduced, assuming it was anything genuine at all?
Here's a Teletext advert from sometime, presumably an older one: