Re: Banning Cyclists
"Therefore unless explicitly allowed there would not be a need to ban them, just enforce the existing law."
Sometimes, it's because enforcing the existing law, especially if it's being flouted on a regular basis, becomes very expensive and may require lots of concrete evidence. Eg the specific law banning the use of hand-held mobile phones while driving. The punishments is an on the spot fine and points on your driving licence unless you choose to try and defend it at court. Prior to that law, existing law already covered it but required a court case every time at much higher cost plus a police officer taking time off from front line duties to attend court as a witness for the prosecution.
This pedestrian zone ban is probably a by-law that can be enforced by a police officer, a PCSO or Council Enforcement Officer by issuing a ticket on the spot.