……… look, a letter to William Pitt from his sister-in-law Mary, Countess of Chatham!

(PRO 30/08/122 f. 174)

Yes, yes, yes, it’s a patronage letter about her brother William, but it’s A LETTER FROM MARY. Rare as anything, these are— so much so that the cataloguer didn’t know for sure it was her (see the pencilled note on the top left of the front page, “Lady Chatham?” — but comparing the characteristic capital M and E in her letter with her signature on her marriage settlement makes me 110% certain this IS definitely her).

Those who know me, and know what a central character Mary is turning into in my novel, will know how excited I was when I found this. Not much to be drawn about her relationship with William (although she does seem to be a bit frustrated about his reluctance to give her request full attention), but it is nice to see that she starts the letter “My dear Mr Pitt” and signs off “Yrs most aff[ectionate]ly, MEC”.

More proof that Mary existed! Yay!