PC or Police Constable: the brave men and women that are the back bone of the Police Service, out in all hours and weather to be selflessly spat at, abused and vomited on by members of the public. I for one salute them especially since I'm now no longer one of them.
DC or Detective Constable (DC): someone who has passed their detective exam and got a nice job in CID or a specialist unit. Try to get here as soon as possible in your career unless you've got your eye on ACPO (1).
Sergeant or Detective Sergeant (DS): Even more exams, even more paperwork, even more responsibility but on the other hand you get to boss people about. If you're friendly you can call a Detective Sergeant by their first name but I like to stick to sarge, guv or boss - just to be on the safe side.
Inspector or Detective Inspector (DI): this is where you get to be in charge of stuff, a shift, a specialist unit, one third of a murder squad. I've been told it's not as much fun as it sounds but I think I'll wait and see.
Chief Inspector or Detective Chief Inspector (DCI): Here you walk the razors edge between the light, ordinary plain speaking coppers, and the darkness, business speak obsessed control freaks. You will be a running a nick or a murder squad, people below you will be coming to you with their problems and will expect you to know what to do, your superiors will be coming to you with their problems and will expect you to sort them out!
Superintendent or Detective Superintendent (DSI): My boss is a DCI, in fact everybody I know's boss is a DCI. I don't know the precise purpose or function of this rank I just bloody well do what I'm told.
Chief Superintendent or Detective Chief Superintendent (DCS): Congratulations you are as high as you can go without selling your soul to ACPO(2). You are in charge of a entire Borough Command or a major specialised unit you definately have your own parking space that much is certain.
ACPO(3): stands for the Association of Chief Police Officers, a dark and sinister conspiracy that is part trade union, part coordinating committee for all the police forces and part NGO. You are inducted into ACPO when you reach the rank of Commander, beyond that are Deputy Assistant Commissioners, the Assistant Commissioners who stand at the left and right of the Commissioner himself, the Deputy Commissioner and finally the Commissioner himself.
(1) I'll explain later.
(3) See I said I'd explain later.