Don't you get it?
He's Lord Monckton.

Come on; we'll go down and straighten out the kinks." So they went down-stairs.

And Forbes tells me that when Thomas acknowledged his identity, Kitty did not fall on his neck.

Instead, she walked up to him, burning with fury: so pretty that Forbes almost fell in love with her, then and there.
"So! You pretended to be poor, and entered my home to make play behind our backs! Despicable! We took you in without question, generously, kindly, and treated you as one of us; and all the while you were laughing in your sleeve!" "Kitty!" remonstrated Killigrew, who felt twenty years gone from his shoulders.
"Let me be! I wish him to know exactly what I think of his conduct." She whirled upon the luckless erstwhile haberdasher's clerk; but he held out his hand for silence.

He was angry, too.
"Miss Killigrew, I entered your employ honestly.