How did Black get into Hogwarts in PoA? (Was: Dumbledore on the Dursleys . .

[pippin_999]

No: HPFGUIDX 151717

--- In HPforGrownups at y
> Thanks, Ammemehr. Please note that any annoyance you may detect in
> this post is not directed at you but at JKR.
> 
> Let me get this straight. No guards or protective spells of any kind
> on the front doors, not even after the first attack proved that Black
> was on the grounds (or could get onto them), and the doors are not
> even taught to recognize Black until after the *second* attack. 
> 
Pippin:
"the walls and grounds of Hogwarts are guarded by many ancient
spells and charms to ensure the bodily and mental safety of those
who dwell within them" -- OOP ch 24 

Hagrid, though he is "keeper of the keys" does not open the doors
for the first years. He knocks and introduces them to McGonagall
before they  enter. I think the doors were already enchanted to
keep out intruders, but either the door spells didn't work against animals,
or they didn't work against Sirius's 'open anything' knife. (He may
also have been trying to use the properties of the knife when he slashed 
the Fat Lady's portrait, not just being wantonly destructive.)

I think there is probably not much even Dumbledore could do to
improve on those spells, and he was probably wary of trying, since
this is ancient magic, little understood, and we know
spells can interact with each other in unpredictable ways.  

There were portraits and ghosts on watch at all times -- why set
mortal guards in a Death Eater's path? Presumably Black wouldn't
have any more trouble eluding them than the ghosts and portraits,
but unlike the ghosts and portraits, they might be killed.

Pippin