Without getting into it the fence has to have a certain standard.
Its fine mesh is so that it takes longer to cut through ie more strands need to be clipped.
The razor wire is obviously there to stop folk just climbing over the top.
I have seen "them" go through a fence like that, to be honest they are pissing in the wind if they think its going to stop anyone with a bit of training who really wants to get in.
It will though however stop anyone that wants to make say a demonstration or is having mental health problems.
I would have guessed the 45 ton truck was set because of an intelligence operation that the ramming a 45 ton lorry through was the method of entry. Similar to the fluids thing for carry on bags. They found out someone was planning to use liquid explosives so had to do something about it.
MAN have always seemed to promote the viewing areas and seem to include them in there plans.
I for one hope this continues, we have usually completed the taxi checks by the firestation and always wave back to the kids if they wave as we taxi past.