[zaphar]

I'm a white, U.S. born, citizen and I read it the first way not the second. The context of "Hello Londoners" makes it pretty clear.

[mikeash]

It will be clear to anyone who’s heard of London’s black cabs (which I’m sure is a lot of people) but it’s probably damn confusing for those who haven’t.

[parent5446]

I'm not so sure. I didn't know what London black cabs were and I still read it as (black cab) driver. I just assumed black cabs meant something like black car cabs, e.g., Uber SUV.

[coherentpony]

I'm confused. Do you think the OP is black?