For future reference, this is what is written in the letter that Luther sent. Presumably only McHaggis really needs to see this, but I'll post it here anyway.

The letter reads:
 
[i]To Whom it May Concern,
 
 It would be best for me not to disclose my name here, as it may easily be intercepted. All that you need to know however, is that I am a high-ranking Death Eater and I wish to join your cause. I don't expect that any of you will trust me, but Mr. Keiper certainly must have, or else you wouldn't have been expecting this letter. If you choose to hear what I have to say, I will be at the Luchino Caffe on Tottenham Court Road in London at three hours past midnight. Coffee (if you so fancy) is on me. Bring as many members as you'd like if you doubt my intentions, I have no plans for anything but conversation.
 
Sorry for "borrowing" your owl,
A Friend[/i]