Green’s Dictionary of Slang

twirl, the n.

1. (UK Und.) working as a fraudulent bookmaker, typically taking large bets but putting them down on a less popular horse – if the originally betted horse wins, the bookmaker simply claims the bettor was mistaken.

[UK]cited in Partridge DU (1961).

2. a confidence trick that involves the substitution of a fake jewel for a real one.

[UK](con. 1950s–60s) in G. Tremlett Little Legs 10: Working the knocker, totting, or doing the tweedle and the twirl.

In phrases

on the twirl

working as a professional thief.

[UK]J. Curtis Gilt Kid 85: There was only one way he knew of getting money. On the twirl. O.K. He was going on the job. He was going thieving.