I didn't realise there was a Cannock V Stafford thing!!
In all seriousness there isn't really.
But you know when a child says something funny and everyone laughs so the child says the same thing over and over and over and over....? But you keep laughing because it's a child?
Then you have a situation when an adult says something that is mildly amusing and they keep repeating it over and over and over?
But because they are an adult and should know better, it stops being funny?
But on and on they go with their repetitive tediously unfunny comments?
They don't realise that they stopped being funny ages ago and have become dreadfully boring, not to mention extremely annoying.
I think that's what the Cannock "joke" is.
As in not really funny any more.