@mpsw
Nature of the event isn't the key thing, though, it is that the event leads to a threat which requires mitigation.
If Harry is not happy with a threat-led approach to the provision of official security, and will only be content with blanket coverage, then it is better for him that he does not come.
I was answering the question, which relate to here as well, when the thread got full.
By that same logic, then Moss should have been told to have a small intimate wedding somewhere else.
Harry could also argue that where he goes he attracts paps and crowds - some unsavoury. I do not know the exact nature of his threat last time, but it seems there are some.
Yes, he is pre-peparing now, (he rightly may not want a last minute threat with baby Lilli and Archie around), but that is all based on past experiences. Perpetrators had been proved to be guilty.
In a certain way, its the same concept that Theresa May and Cameron ( I can understand Blair, the others I don't know much of anyone having real threatened them) have protection naturally as you don't want to act after the fact.