Might be ex-patriate, but it's safe to assume that people in London are british unless told otherwise...
I’m British, and I lived in London for 6-7 years. It is not safe to assume that. Central London is incredibly diverse.
The author now says he was born and raised in London.
Doesn't matter, it's still a 2/3 chance that someone saying they live in London is British. That's not such a crazy assumption, especially as a software developer.