What exactly is Dennis' role in prison in Starred Up?

Question

During my second viewing of Starred Up (2013), some scenes piqued my curiosity. Dennis clearly is the prison boss who everybody in the prison is afraid of. Even the guards take their cue from him. But apparently he is a prisoner and lives in a cell in the same building as other inmates, so how does he have such clout in the prison?

Scene 1: About a quarter into the film Neville goes to report to Dennis at a location separate from the main wing after threatening another inmate. Interestingly he has to wait outside a room/cell marked "9 CLASSROOM". There is a guard standing guard outside the room. Neville waits a bit and goes in only after two guards come out and Dennis shouts "Next". So Dennis counsels the guards? Can prisoners do that?

Dennis to Neville: Your youngster, what I've heard. No offense to family but the kid's causing unnecessary to the good order and discipline of this jail. And lock downs, as you well know, cost me money.

So Dennis, a prisoner, funds the prison? What does he care about commotions or lock downs? Why do they cost him money?

Scene 2: A little later the head of the guards Haynes comes to see Dennis in his cell secretly and slides a bulging envelope under his pillow and goes:

Haynes to Dennis: Selfy's got a stomach bug. (Selfy is another guard)

Dennis: Like the old days.

Haynes (a little surprised, stops in his track and turns): Got to keep the show on the road, Dennis.

I don't get this scene either. Why does the deputy governor have to bribe a prisoner? What is Dennis' role in this prison?

Answer 1

He's the prison CRIME boss. He earn moeny by smuggling in and then selling stuff that are illegal. Lockdowns cost him money as he can't do his businees and during searches some of his cargo might get exposed. He pay guards but guards need to look like they're doing their job from time to time so they will report "something".

The guards also pay him money because he have contanct with outside underworld. Therefore he can get them things. Also, a good businessman, would employ the guards to do some things. Then not only he bribe them but make them compliant in crime. And then he can use this as a leverage for extortion.