This is a huge load of bullshit. 99% of the "banking programmers" are some of the worst coders in the world. A vast majority of them just babysit a Bloomberg terminal, barely understanding the supposed math they use all day. Others just babysit an Excel spreadsheet, or worse, develop whole applications in Excel then try to get a real programmer to "build it". The lower echelons are even worse and just make shitty C#…
Maybe it's different in London compared to NY. There's plenty of decent makers in Finance in London. There's people who use all the best practice techniques in software development. People who wrote code you use every day.
I've seen the kind of guys described in zed's first para, in Finance in London. I don't think it's different, but YMMV.