P.A.C.E. Stands for Police and Criminal Evidence Act 1984.
Since the date of 1984 as shown there have been many changes additions and sections added to P.A.C.E. allowing more power to the police but at the core the rules stay the same. Although these changes are represented as being for the betterment of the public they are still guidelines with wider interpretations for the police to use, as they will, not necessarily in the publics interest. It will be used and abused by all ranks of police officers from the top of the pile to the bottom and their actions you will find are always backed up by ambiguously phrased police statements.
This Link will take you to the Gov.UK site for more information or research.
My personal experiences with the police show the codes are frequently missunderstood or ignored or that the officers concerned feel no need to use them as they (The Police ) obviously need educating with regard to the meaning of the act and how to carry ut any action needed to enforce it.