It may come as a bit of a surprise, but when I worked in Broadcasting House in the 80s and 90s, the switchboard took several bomb threats every day. Of which they were almost all false ones.
I suspect that many of those were for either LBH or TVC, and so it is not impossible that occasionally there would be one which had a more authentic ring to them than the usual crank ones.
So if there is any truth to these rumours whatsoever, then there may well have been some substance to them.
However, as you say, the entire thing is a moot point as the BBC never said that - so what is the story?
Well, that nobody in the Beeb would have gone "Noel won't do it, let's pretend it's a bomb", as was suggested. In the One Day In The Life Of Television book from 1988 one of the contributors is the Head of Security at BBC Belfast, whose diary for the day is a long list of security checks, suspicious vehicles and bomb scares, at one point being told that they'd been phoned up to warn them of a bomb but he was pretty certain it was a hoax and didn't evacuate the building, suggesting that kind of thing happened most days.
Obviously, glad everyone involved at Thames Euston got away with no injuries from what could be a far nastier incident, but was David Frost even working for Thames at the time - or did the purputrator end up going to completly the wrong London franchise?
As the story briefly mentions, she was convinced that Eamonn Andrews was in on the whole thing as well.
I heard Tom Edwards relate a story from the 80s, where someone turned up at Thames, and asked to see an announcer.
Tom was available, and he went to reception to see them, where he was promptly smacked in the gob because Thames had rescheduled Falcon Crest (I think ?) to a different time slot
There's a story in Peter Sissons' autobiography about when he was at ITN and was told George Harrison was in reception, an old friend of his from school of course. He was with a group of hare krishnas and George told him he had a big story which had to go on News at Ten that night, and when Sissons asked what it was, he said "Peace!", and then walked out again.
It's worth remembering out how quickly things must have moved within those 55 minutes to go from just delaying the show, to the show not happening, to having Noel in the broom cupboard to (sort of) explain things. That they managed the latter shows some remarkably quick thinking to try and shore up one of the Beeb's biggest shows not airing. Though it is curious the nominated standby was a Christmas special...yes it's still Noel, but not entirely seasonal as he alludes to in the NC1 link. I guess it wasn't entirely unusual at this point. There were however no House Party compilations to use at this point - it is likely they would have used these had it happened from the following series. And of course they did, in January 1998, though they had a little more notice that time.
Yes, and of course it was the Christmas Presents from 1991, because 1992 was the one year of the nineties when Noel didn't do a Christmas Presents show, with the House Party live on Boxing Day instead. I know that it used to be the case, probably still is, that every live show would have a standby scheduled in case it couldn't go out for whatever reason, as near enough to the actual show as possible, and presumably that was the most convenient pre-recorded Noel show available. I seem to remember Inspector Sands of this parish saying there was one standby show which was faithfully scheduled and laced up ready to go dozens of times, for months and months on end, and when they finally had to broadcast it, it wouldn't work because it had been standing by on pause for so long, the tape had been damaged.
There's an interesting comment under that video which suggests that one reason why they never did the show in the end was because there was obviously an audience who all had to be evacuated, and by the time they had the all-clear, most of them had already long since gone home. Certainly House Party was such a big show for the Beeb at that time they'd have happily cleared the schedules for it whenever they were able to do it - and they had a lot of time, it was on at six o'clock that week - so clearly it was just impossible in the end.