"For the truth of every thing here related, I can appeal more particularly to the testimony of Colonel Fitzwilliam, who from our near relationship and constant intimacy, and still more as one of the executors of my father's will, has been unavoidably acquainted with every particular of these transactions. If your abhorrence of me should make my assertions valueless, you cannot be prevented by the same cause from confiding in my cousin; and that there may be the possibility of consulting him, I shall endeavour to find some opportunity of putting this letter in your hands in the course of the morning. I will only add, God bless you.

Darcy encourages (perhaps too strong a word) Elizabeth to seek out CF, should she not believe any of his story. I have no doubt that CF doesknow every particular and that FD would not have said "if she asks, put in a good word" - I think his honor would revolt at such arts... however, what I do wonder is how would he have explained to CF that EB may ask him some questions? I don't believe that CF would have voluntarily discussed Darcy's detailed business, particularly Ramsgate, with EB (or anyone else!) otherwise (gossip is another matter). I suppose he could just say something along the lines of "she was deceived by Wickham so I set her straight, she may ask you for confirmation and you have my permission to discuss it" as opposed to "she hates my guts though I love her passionately and she refused my offer of marriage!"