Arlington Street, April 12, 1764.
. . . You will have heard of the sad misfortune that has happened to Lord Ilchester by his daughter's [Lady Susan Fox's] marriage with O'Brien the actor. But, perhaps, you do not know the circumstances, and how much his grief must be aggravated by reflection on his own credulity and negligence. The affair has been in train for eighteen months. The swain had learned to counterfeit Lady Sarah Bunbury's hand so well, that in the country Lord Ilchester has himself delivered several of O'Brien's letters to Lady Susan; but it was not till about a week before the catastrophe that the family was apprised of the intrigue. Lord Cathcart went to Miss Read's, the paintress: she said softly to him, "My lord, there is a couple in next room that I am sure ought not to be together, I wish your lordship would look in." He did, shut the door again, and went directly and informed Lord Ilchester. Lady Susan was examined, flung herself at her father's feet, confessed all, vowed to break off--but--what a but!--desired to see the loved object, and take a last leave. You will be amazed--even this was granted. The parting scene happened the beginning of the week. On Friday she came of age, and on Saturday morning--instead of being under lock and key in the country--walked down stairs, took her footman, said she was going to breakfast with Lady Sarah, but would call at Miss Read's; in the street, pretended to recollect a particular cap in which she was to be drawn, sent her footman back for it, whipped into a hackney chair, was married at Covent-garden church, and set out for Mr. O'Brien's villa at Dunstable. My Lady--My Lady Hertford! what say you to permitting young ladies to act plays, and go to painters by themselves?
Poor Lord Ilchester is almost distracted; indeed, it is the completion of disgrace--even a footman were preferable; the publicity of the hero's profession perpetuates the mortification. Il ne sera pas milord, tout comme un autre. I could not have believed that Lady Susan would have stooped so low. She may, however, still keep good company, and say "nos numeri sumus"--Lady Mary Duncan, Lady Caroline Adair, Lady Betty Gallini--the shopkeepers of next age will be mighty wellborn . . .
-from Selected Letters by Horace Walpole selected and edited by William Hadley (London: J. M. Dent & Sons, 1963.) Everyman's Library No. 775. p 86-87.