Green’s Dictionary of Slang

excellent, first-rate, admirable.

1856		‘A Harassing Painsworth’ in Yates & Brough (eds) Our Miscellany 27: ‘He's a rank scamp,’ said one — a gentleman sitting near to the chairman. ‘A wicked dummy hunter,’ said a second. ‘A fly mizzler!’ said a third.
1884		J. Harrison ‘Negro English’ in Anglia VII 262: Rank ez anybody = as well as, &c.
1925		N. Lucas Autobiog. of a Thief 175: Clements was a rank bad ’un.
1978		D. Hebdige Subculture 163: ‘Rank’ was a term of approval.
2000		Guardian 14 Jan. 21: Da fashion victim (black, white or whatever) who ‘tends to be clever cos ’e wears rank, over-priced gear’.