Emergency Alert System

I doubt it - that would come under several exemptions.

No, they were just treated as major news stories and the schedule was adjusted accordingly. Of course it's alot easier for the BBC now as they already have a rolling 24-hour news operation which simply simulcasts on BBC One. I'm sure ITV would struggle in the event of another 9/11 or 7/7.

I think the OP was asking about what would happen during a major national or international crisis which threatened normal day-to-day government and caused the breakdown of society. Were talking about nuclear war, aliens landing, rampant infection (as in "Shaun of the Dead" ) - that sort of thing.

Not a nice prospect, but they have to plan for it. After all, you don't want to be hiding in your loft/cellar/garden shed listening to the scheducled recording of "The Archers" when your neighbours are being vapourised by immigrant aliens.
(EDIT: By "immigrant aliens" I don't mean the Albanian Family living at number 34!)

I once saw the ALERT message on my car radio when flicking through the dial. It seemed a pirate station was using the function. IIRC, the display flashed the word 'ALERT' and the volume went up (in the same way as during a TA announcement).

Having worked in numerous radio studios over the years, both commercial and BBC, I've never seen any function to activate an Alert message on RDS. As you say Orry, it's possible the BBC may activate the system centrally across its network. As for ILR stations, I wonder if the operators of the transmitters such as Arqiva and Radica have control of the function, on the say-so of the government.

Or could it be that it's just one of those possible functions on RDS like the 'News' flag which is completely unused in this country? After all, not everyone listening to the radio is going to have RDS.

Well I've said it now, and no one has come round to carry me off to the Tower! (or had the post deleted)

Did any of that happen, BTW, or did they fix it in time? I don't remember, I managed to avoid all coverage of the QM's death (partially as a result of reading that very article, partially blind luck).

more on that story later

Correct: all that happened in those cases was that BBC1 came out of the schedule, and after a brief announcement over a "News Report" slide, crossed to N24. Radio news did it differently on 7/7 - I can only remember Radio 2, because when Ken Bruce was on, the news was starting to come in that it was a terrorist attack. Jeremy Vine started discussing it with him before his 12pm show started, which was of course when the PM made his speech. IIRC the first reports came in from around 9am of a power surge on the Underground, which the travel presenter read out normally - until there were reports of an explosion on a bus.

Before N24, BBC1 would come out of the schedule, have an announcement over a slide, before crossing to the newsroom. There would occasionally be a brief sting before the picture cut to the newsroom. In VERY exceptional circumstances (eg Diana's death), BBC1 crossed to BBC World overnight after closedown.

RTE did a 2 part drama about 2 years ago called "Fallout" . It was about what could happen if there was an explosion at Sellafield and wind carried the material to Ireland.

The trailors were dropped after a few days because they began with the BBC N24 presenters announcing "fears of lastnight's Sellafield explosion resulting in Ireland's Chernobyl".

But with no trailors broadcast for a few days before the show, non-digital (and even some digital) viewers could be forgiven for mistaking the BBC News 24 footage and RTE News Specials (despite using actors as presenters and using a weird backdrop) for reality. CAs reminded us every 15 minutes that we were watching a drama that contained fictionalised newscasts.

If only that would happen on the BBC

I'm sure I heard that the BBC have a hidden nuclear bunker somewhere to be used in the event of major incidents to broadcast the BBC ouput across both radio and television. Is this actually true?

Was it the BBC or the government that had that Y2K bunker?

TV's backup plan for TV Centre being unavailable was for Pebble Mill to take control of the network, as per that night when the six fell off air due to a power cut.

The bunker you refer to is probably Wood Norton, which was radio only as a backup centre - http://www.subbrit.org.uk/rsg/features/sfs/file_16.htm

In addition many of the local authority bunkers had BBC studios in them, but exactly how they would have been used isn't quite clear.

I seem to remember ILR (circa 90's) had an obit alarm (obituary alarm) built into the console which would buzz and flash. When it went off you were supposed to switch to IRN to find out who had died or what emergency had taken place. The only time I remember it going off was when Margaret Thatcher resigned. I Don't know if that still exists as this was in the days when we had the Radio Authority and not the piddly poor excuse for a regulator we have now