The Code

According to Sky News Newsdesk on Twitter,

Coded warning issued of Irish Republican dissident bomb in Central London.

Now, here's something that always bothered, baffled and befuddled me.

What's the code? Who decides the code? How does the code get delivered to the people that need to know the code? Is there some sort of honourable back-channel communications between MI5 and the IRA/Splinter groups where they decide that if someone uses the word "orange" at the same time as saying there's a bomb then it's genuine?

I understand, I think, why the warnings are coded. It is so you can filter out the hoax call from the real thing. As I say though, that means at some level, somewhere, there is a gentlemanly chat where each side decides on what the code should be doesn't it?

I don't expect an answer from anyone on this. It just always makes me chuckle when I imagine terrorists and spooks agreeing on certain words to ensure the latters threats are considered credible.

Update: Just found this.

The procedure for organising codes has been long established. Codes alter periodically by agreement between the Provisionals and the security forces, both sides knowing that a failure in communications could be catastrophic. The IRA pass on a chosen name to the Gardai in Dublin, who in turn give it to the RUC Special Branch in Belfast. From there it is disseminated to forces on the mainland. Liaison is also held with a number of news organisations.

In Northern Ireland, however, the complication is that the IRA are not the only bombers. Because of the number of factions, up to six code-names could be in use at a given time.

None of the paramilitaries who wants to establish a bomb code is turned away.

I wonder if you can apply online in this modern world?