We have caller display on our phones but quite a few of the people we want to talk to choose to withhold their numbers too. Among the people who have withheld numbers are my mum's home, my mum's 80 year old friend, my brother, my ex Sil who is currently having problems, her daughter (who is one of her problems) but, so far today, I have answered 8 cold callers with 'number withheld" on the screen!
To think that London, or anywhere else for that matter, does not belong to any one demographic