Rotherham fan vs Greg and Terry.

cafcfan

This article talks about how "ambient noise" has dramatically reduced the reach of Bow Bells. wired.co.uk/article/bow-bells-cockney

cafcfan

Here's the actual map comparing 1851 to 2012. It's of note that the bells' sound travels to the North with very little impact south of the river.

seth plum

Fill yer boots:

http://public.oed.com/aspects-of-english/english-in-use/cockney/