I think if they have a thick east end accent then it is clear that they come from the east end.
But as 'swipe says below, you could always pose the question to ask about their origins. People often like to talk about that sort of thing.
Just don't get my mother started on genealogy though, she can bore for England on the subject.
( tangledupinblue hairy badge with moving eyes, Tue 8 May 2012, 9:43, 2 replies, latest was 12 years ago)

to be honest, it's a question i ask nearly every new person i meet regardless of accent/clothes/colour/job etc
i'm always interested to learn about people's backgrounds.

you know, just to check they are fit for me to associate with......
( rachelswipe with a fork, Tue 8 May 2012, 9:45, Reply)

She can also suck cock for England,
and indeed will be doing so this very summer at the 'twenty twelve' Olympics.
( Monty Boyce, My cheese game is strong, Tue 8 May 2012, 9:51, Reply)

She is considering having her teeth removed specially for it.
But needs to check with the IOC to see if this is permitted under their rules.
( tangledupinblue hairy badge with moving eyes, Tue 8 May 2012, 9:55, Reply)