Regency romance - spy hero and heroine. Spoilers.

[Olivia]

It's driving me crazy!
Regency romance
Hero is known to be a spy
Heroine is presented at first as a slightly older debutante (25ish?) looking for a husband, but is later revealed to be a spy also and her letters to 'mother' were in fact to her spymaster
Spymaster himself gets a romance in a later book in the series
The scene I remember most vividly is her undressing for him in a carriage 😳
All the main terms are too generic for Google to help me, I'd love to remember what this is called!

[Lobstergirl, au gratin]

When did you read it?
Where is it set?
Erotic or explicit?
What country?
Paper or ebook?
Cover?

[AdoraBelle42]

Lauren Willig has a regency series with spies starting with The Secret History of the Pink Carnation.
I only just started the first book and don't think it's this one, but maybe one of the later ones?

[JennyG]

Brazen Angel by Elizabeth Boyle?

Brazen Heiress by Elizabeth Boyle?

[Summer]

Try looking through the solved books folder, I have a vague memory of a book like this showing up in this group.