Do I have clearance. Let me think about that. I have certainly been in there, but someone else escorted me back.

I paid attention to the wards and so on when I went in that time. Not because I was planning on breaking back in to destroy the archive, mind you, or I'd have paid better attention. I THINK I know the sequences and spells. Though this was -- six months ago? -- they might have changed them.

Alternately, depending on where you started the fire, it might not matter. Dogstar's talked about burning the entire Ministry down, though nothing's ever come of it.