Yeah, I remember Mr Banks, as others have said, it was a general security announcement for the stewards, as was the spinning/flashing light (different colours to represent different types of emergencies).
I "worked" as a steward for less than one match (the 1st sky game against QPR) but sacked it off after about an hour.
Was told that my duty was to stand outside the main stand directing people to their entry points but then when the match kicked off I was supposed to keep standing around outside the main stand all match to make sure that nobody climbed over it (?) and got in for nowt!
"Errrrr, OK boss, I'll get on with that right away" - Went to my car, got changed and used my ticket to watch the match instead.
There were other coded names that represented other specific emergencies (Mr Burns for a fire ...etc) but it's so far back in time I can't remember them. Remember there was one for a bomb but can't remember the guys name.... Mr BIG-FUCK-OFF-BANG! or something like that :)