Oh! The Silbury thread has been locked - I thought the discussion was productive. I had something to add about 'trespass' so I'll just add it here as a little addendum (as Silbury is a SSSI).

Criminal Trespass
People who cause damage while trespassing may, in the process, commit a criminal offence
(e.g. of criminal damage of property under the Criminal Damage Act 1971) but trespass is per se not normally a criminal offence. Trespass is a criminal offence in some cases, for example on railway land or where military byelaws are in force.
Another example of criminal trespass is where land has been notified as a Site of Special Scientific Interest; a trespasser may, in the process of trespassing, commit a criminal offence under Section 28P of the Wildlife and Countryside Act 1981, if they (without reasonable
excuse):
- intentionally or recklessly destroy or damage any flora or fauna or geological or physiographical features by reason of which the land is of special interest;
- intentionally or recklessly disturb fauna; and they knew what they had destroyed, damaged or disturbed was within a SSSI. Indeed, any person, whether a trespasser or not, who intentionally causes the damage noted above is also likely to be committing a criminal offence.