Breaking in and damaging property are separate offences to trespass. Trespass on land by itself is not a criminal offence. Prevention of trespass and the removal of trespassers are the responsibility of the landowner and not the police.
If the police were able to attribute any damage to one or more individuals they could be prosecuted through the courts but their punishment would not be eviction of the whole encampment. This is because British Law only punishes the wrongdoer, not their family, friends, or the whole community. Also, under Human Rights legislation, punishment must be proportionate. So while a person could be fined or imprisoned for criminal damage, it would not be reasonable to impound their home, prevent their legal employment or disrupt the education of their children.
Breaking in and damaging property are criminal offences which are investigated by the police. They will be subject to sufficient evidence and witness statements. Witnesses would be required make a statement to the Courts confirming that they can identify the person(s) who caused the damage.
If you see any criminal activity being carried out by any member of the public, please report it to the police by phoning 101.