He also appears to know something about the fighting ring based around the Tiger Docks in London - specifically he has been sending 'unnamed criminals' to be 'dealt with properly' by the allies of 'Von Richter'
In September 1893, in a stake out of a gentlemen's club, Rigg was spotted by this police sergeant, who immediately recognised him then had him shackled and taken towards the police station. Carmen distracted the guards long enough for Garvin to sap one of the Sergeant's colleagues, then Carmen in turn dazzled another by forcing the constables own hat over his eyes.
With two battered constables left in a near by street, stripped of their uniform and whistles, and the Sergent on Rigg's shoulder (also declothed and dewhistled) they took the man back to the Dagger and Sheath where they awaited the carriage.
After some complications with the telegrams, Hobson later turned up with the carrriage and Mrs MacTannon.
The Sergeant was tied to a practice dummy in the training room. Garvin had turned his back in order to get the ladies out of the room, while Rigg was putting his knucks on. However, no one saw Morag try to take off the Sergent's ring. In a mighty bright blast, Mrs MacTannon was severely burned on her hand, while the Sergeant screamed in pain and convulsed.
Garvin rushed Mrs MacTannon to Dr. House for emergency treatment, leaving Rigg all alone with the dying Sergeant. Feeling bad that he didn't get his own back, Rigg thumped the Sergeant in the stomach three times to make sure he was dead, cracking a rib or two in the process.