If nothing happens, complain that he should have paid out
So named as 1 arm is much larger than the other due to the amount of repeated 'stroking' of other mens cocks it performs, usually for £5 or less.
Gayboy 2 - "OK, but you'd better not have a go on the One Armed Bandit while you're in there!"
Gayboy 1 - "I won't I promise, girl"
Normal bloke from the North - "You queers disgust me"