Paul Terry wrote

Edward was referring to Vauxhall, which comes under SE11 (Kennington
postal area). It is adjacent to SW11 (which is Battersea).

The way that London postal district numbers developed has a strange
logic, largely based on the location of head sorting offices (and the

whims of Anthony Trollope).

Possibly, but blaming someone who died in 1882 when postal district
numbers didn't become part of postal addresses until 1932 or so seems
more legend than fact.

And indeed SW8 (Nine Elms) lies between SW11 and SE11 so they are not
adjacent.

--
Mike D