Business as usual.

I've been trying to track down the origin of this phrase with no luck as of yet - any ideas out there? Thanks...v

Perhaps it was a remark made by a lady of the night when told to "F-k off!"

Tat is, after all, the oldest business...

It was a very common sign in bomb damaged shops in Britain in WW2, and used to indicate that, in spite of the damage, they were still open for trade.