...The Queen's English is pretty much identical from Christchurch to Aberdeen, but you can find half a dozen distinct vernacular dialects in London alone.
That's what I'm talking aboot: in Russian it's not the case. Frankly, there never was a big variety of dialects here. Historically there were two major dialects: Kievan and Novgorodian, (the latter is considered by some linguists as a seperate branch of East Slavic language). Then there was also ceremonial Church Slavonic based on Kievan, influenced by liturgical Bulgarian. Modern Russian is based on Kievan dialect, and as far as we know, it remained pretty uniform up until Peter, who majorly reformed the tradition of administrative language, so it looked less like liturgical. It changed significantly in 18th century, with new, more "civil" forms of it and later was more firmly established during the "golden age" literature of 19th century.
Nowadays all the difference you have is a few pecularities with pronounciation, a few archaic words here and there, but that's about it. I dunno how that was achieved in particular, but there wasn't too much struggle, iirc.
But that's the thing with Slavic languages: knowing one, you more or less is able to understand all of them in written form, even the dead and obsolete ones. Strange how we manged to keep it that way without much effort.
...The Russians got rid of their dialects and it comes as natural to them to speak standard language and slang only.
True, more or less.