SOLVED. Historical Fiction about mistress of royalty, possibly set 19th century [s]

[Briar Rose]

Hi, I'm looking for a book I listened to in audio format about 8 years ago. I think the paperback was probably published in the 1980s or 90s, but could be earlier. It's a fictional work based on the real life of the mistress of an English Duke. (I don't know how closely based). It's set in the late 1700 or sometime in the 1800s.

Plot details I remember:
She becomes his mistress, and he gets a role in government like Master of the Horse or some such. They live in a beautiful house together at huge expense and he uses his government position to trade favours in order to get extra income. It may have been set during the Napoleonic wars? After they break up, he leaves her with nothing.

She's then involved in a court case against him as a witness - it's some kind of libel suit I think? The details of their affair, their lavish lifestyle, and the glad-handing is outed. There is a huge scandal. That's all I can remember.

If anyone can point me to the book, I'd really appreciate it. Thanks!

[Briar Rose]

Oh, nevermind, I found it! It's Mary Anne by Daphne Du Maurier. Unbelievable. I've been searching for this book for about 3 years and 5 minutes after I post here I find it.