Offer him recompense, then betray him
This page contains details about Fallen London Actions.
Inform him of an even richer target, but warn the Constables of his intentions.
A rival removed
"You're a decent sort," he growls, with a nod. "Bloody decent." He goes off whistling.
You hear of his arrest two days later. The Constables were not gentle; apparently someone suggested to them that the Broken-Toothed Cracksman was Jack-of-Smiles.