It's probably well before your time but a number of comedians were using this expression (including "The Goons") as what would be called a racist term these days alluding to the number of migrants coming into this country and settling there. There were also similar remarks made at the time regarding Bradford and the number of people from Pakistan who were settling there. The joke of the day was when they were asked what occupation they would be taking up in Bradford everyone would reply "Doctor". One of the officials became a little suspicious and asked "What sort of Doctor are you"? and received the reply "Bus Condoctor"!
