That's a lie, the protesters did try to occupy Paternoster on the 15 and the police only kettled them when they stopped outside the entrance of Paternoster and started chanting the streets were theirs - at which point the police feared the protest would turn ugly which is not surprising if you remember how much damage the riots - which started out as a peaceful protest too - did in August. When he tried to break through the barrier, Jody Mcintyne was approached by several police office who tried to push him back although he was not pulled from his wheelchair. Of course that wouldn't have happened if he and other protesters had listened to the police and settled down instead of chanting angrily and trying to push through the barrier...
Kafka, the people of the protest understood they weren't able to occupy Paternoster Square and didn't make an attempt on occupying it. The real problem is they were kettled, shoved, punched and one video showed a disabled man being pulled from his wheelchair. At was, as I repeat, a peaceful protest.
People were not allowed to occupy Paternoster Square because the square is private property and the owner didn't want to allow protesters there. The police are just doing their duty by protecting our fundamental right to private property, how would you feel if a group of people just barged into your house and refused to leave? Wouldn't you call the police and expect them to protect you too?