See, I don't mind that. But then it was a constant when I worked in an office in Leeds in my formative years.
Somebody you couldn't stand probably used it. I had an uncle who was an alcoholic pillock who always said "Nar then" as his first words to greet people (i must've been about 7 or 8 at the time) and its something I really dislike hearing now. Though to be fair, it's not a common thing round this way.