"While all East Enders are Cockneys, not all Cockneys are East Enders." (https://en.wikipedia.org/wiki/Cockney)
Map of areas within earshot of the Bows Bells. Green area represents 1850 while the blue area represents 2012. Capacity to hear the bells diminished as ambient sound increased courtesy
A true Cockney is someone born within earshot of London's Bows Bells which peal from St. Mary Le Bow Church in the city's centre. In 1850, anyone living six miles to the east, five miles to the north, three miles to the south and four miles to the west of the Bows Bells was considered a Cockney. My great-grandma, Daisy Blay, who was born in St. Pancras about two and a half miles from St. Mary le Bow Church, was a true Cockney.
Cockney, meaning "cock's egg", was originally a pejorative term to refer to any working class Londoner."Those who could claw their way above the poverty line soon moved out -- aided by the arrival of the railways -- leaving behind the highest concentration of the poor and underprivileged anywhere in London." (http://www.history.co.uk/study-topics/history-of-london/east-end-land-of-the-cockney)
Crime, drunkenness, immorality and violence were common in Cockney London, culminating with the grisly murders committed by Jack the Ripper in 1888 in Whitechapel. Despite the hardships, Cockneys developped the reputation of possessing an indomitable spirit and a good sense of humour.
Cockneys created their own rhyming slang, originating with the costermongers, or street traders, in the 1840's. "Telling porkies" referred to pork pies which rhymed with lies = telling lies. "Have a butcher's" referred to a butcher's hook which rhymed with look = "Have a look."
"It's that Cockney humour -- a sense that goes all the way back. People have just been bombed out in the Blitz, but they put on a smile, they get down to the pub. It's the heritage of the East End." (http://www.telegraph.co.uk/tv/2016/02/29/the-history-of-eastenders/)
Cockneys reasoned that if they could survive the poverty, survive Jack the Ripper, survive the Blitz, they could survive anything. My grandma had that indomitable spirit inside of her. The daughter of a woman who was so poor, she sold all of their furniture save one broken chair, my great-grandma was quite familiar with poverty. Yet she was rich in spirit; she had so much love to share. Sadly, the one thing she did lose was her cockney accent, so that Canadians wouldn't know she was a home child. But she remained a true Cockney.
St. Mary le Bow church bells were damaged during the London Blitz, but were repaired, courtesy https://s-media-cache-ak0.pinimg.com/236x/b4/80/e5/b480e54764726a6f1b08bd543887ec59.jpg.