Green’s Dictionary of Slang

Swell Street n.

[swell n.1 (1) + SE street]

the West End of London.

[UK](con. 1737–9) W.H. Ainsworth Rookwood (1857) 178: Soon then I mounted in swell street high.
[UK]G.W.M. Reynolds Mysteries of London vol. 2 142: Swell-street The West End.
[UK]Hotten Sl. Dict.

In phrases

in swell street

well-off.

[Aus]Vaux Vocab. of the Flash Lang. in McLachlan (1964) 273: A family man who appears to have plenty of money, and makes a genteel figure, is said by his associates to be in swell street. [Ibid.] 277: [...] a man who is in swell street, that is, having plenty of money.
live in swell street (v.)

(UK Und.) to live a prosperous, respectable, secure life.

[UK]Farmer & Henley Sl. and Its Analogues VII 459/2: to live in Swell-street, to reside in the West End.