Of course back in the past when the TV landscape was different you would have great chunks of programming that wasn't allowed to have commercials all over it. Schools programming is the classic example here, some religious programmes and one or two other things.
There were always exceptions to the rules though - the original run of the Krypton Factor for some reason lost in the mists of time went for quite a while without an internal ad break, but I think Granada's hand was ultimately forced in the 1990s, and then I presume it was twisted right off for the 1995 series but we won't talk about that.
That’s interesting about Krypton Factor. A few half-hour programmes didn’t have ad-breaks, yet other programmes scheduled in the same slot did. The programmes in the 7pm Wednesday slot (This is Your Life, Where There’s Life etc) tended not to have an ad break.
CEEFAX SUBTITLES BEGIN SHORTLY