I presume he means he has the mathematical aptitude to teach high-school math, which (at least in my area) maxes out at trig in most schools and Calc 1 in the bigger ones.
To teach as an adjunct, that's about all you need to teach. If you want to be good at it, some genuine compassion for your students will help there. If you want to be awesome at it, you'll typically need the above plus some training in the proper ways to educate, motivate, etc.
If you go to the London hipster map. I live square dead in the middle of it (the Shoreditch triangle). Granted I've only lived here for 4 months but the only 2 bad things that I've seen were:
1) Someone puked in the alleyway that leads to my door. I walked around it.
2) One day when coming home at 11pm, there were people smoking weed in front of my door and one guy was pissing against the building close to my door. I went inside and everyone minded their own business.
Yeah those are not the nicest of experiences, however I'm rewarded every day by incredible access to art & culture (and amazing music gigs I can walk to by foot) and -- plainly -- I love people who step outside normalcy in terms of how they dress & express themselves. It's fun to see and makes me push my own boundaries :)
EDIT: Shoreditch is by now also an incredibly safe & affluent/expensive area. Never once have I felt threatened here, I feel safe carrying my phone on me at all times of day/night. This might be different in the cheaper-but-also-hipster areas of Hackney like Dalston.
This was shoreditch. Don't forget between city road and shoreditch is one of the worst estates in London. You must have been lucky but we had constant problems 2-3 times a week.
Sold up and bought a nice place in Strawberry Hill for the same money and am awarded with peace and quiet and literally zero crime and antisocial behaviour. Everyone is either financial and/or tech, legal or medical as well.
Fellow Austrian here. I was in your exact boat about 6 months ago. Startup "scene" in Vienna is sad. Immigrating into the US is hard so I looked at Berlin and London.
For now I'm living in London. I considered Berlin, but I think the English practice here is invaluable. My English was already quite good when I came here, but it's improved LOADS. Also there's much more going on in general (culturally, socially), and there's more and bigger startups here (e.g. compare HN Who's hiring / startup city rankings).