Green’s Dictionary of Slang

(UK Und.) awaiting a promised event, a bribe, a tip-off etc.

1968		G. Slatter Pagan Game (1969) 163: Making his marble good with the missus. Definitely on a promise.
1977		G.F. Newman Villain’s Tale 176: ‘Did all right, did he?’ Lynn was unable to resist that. ‘Fucking slaughtered him. Reckoned how him and Pyall had a deal, Pyall had put him on a promise. He did terrific.’.
1989		J. Morton Lowspeak.
2006		D. Seabrook Jack of Jumps (2007) 239: He seems to have believed he was on a promise.