Had Robin Hood not been filmed there, no one would have even heard of the place.
Its hardly the Pyramids is it? The wall suffered minimal damage, its a very small dry stone wall, the type of which is found all over many landscapes around the UK.
No one is saying they shouldn't be punished either.
But imho prison should only be for the most serious of offences, in itself, felling a tree, with a TPO, is a finable offence, up to £15k.
I think a 2 year community order with a large fine, working for the NT would have been a better punishment, done them a lot of good and saved the tax payer too, these men are apparently skilled tree surgeons, their skill set should be used for the benefit of the NT and the countryside, whilst also providing a suitable punishment.
BTW if the sentencing guidelines prevent this, maybe they need to be changed?