Green’s Dictionary of Slang

promoter n.

[the fraudulent schemes he ‘promotes’; note Holyoake, Dict. (1617): ‘A promotour, which, having part of the forfeit, bringeth men into trouble’; Nares, Glossary (1822), defines promoter as ‘an informer’]

a confidence trickster.

[UK]J. Day Ile of Guls III i: lis.: These are notable knavish courses. What breeding hast had? man.: Very good breeding sir: My great Grandfather was a Rat-catcher, my Grandsier a Hangman, my father a Promoter.
Holyoake Dict. n.p.: A promotour, which, having part of the forfeit, bringeth men into trouble.
[US]A.J. Liebling ‘The Jollity Building’ Just Enough Liebling (2004) 257: The promoters, the fellows who are always trying to earn, in the local idiom, a soft dollar.
[US]Goldin et al. DAUL 164: Promote. 1. To swindle by high pressure means; to give, or use the promote. [...] Promoter. One who promotes.