Hello my name is Alex and I will help you.
You should report this to English Heritage who will investigate the complaint.
Therefore you should not report it to the Police.
This is not a criminal matter per say. That is its not as if it is theft etc.
So the Police won't investigate this.
This is a matter governed under slightly different law.
You have no duties. Once you report it your work is done
English Heritage can consider the matter, investigate and prosecute by serving enforcement notices etc where appropriate.
Can I clarify anything for you about this today please?