The Secret Duke by Jo Beverley

The Secret Duke reached #16 on the New York Times best seller list for Mass-Market Fiction.

The Secret Duke was first published on 1st Apr 2010 by Signet [9780451229533].
It became available as an e-book, 26th Jun 2010.
An audio edition was published on 22nd Jun 2022 by Tantor Media [9781666130584] for download only.

More info is available here:

The Duke of Ithorne might be a rake in some respects, but he is every inch a duke. He takes his immense responsibilities seriously, and also his place at the heart of political and court power -- a place already taken by the Marquess of Rothgar.

He values his escape, however, his alter-ego Captain Rose of the Black Swan, sailing out of Dover on coastal trading voyages, and occasionally on missions for the Crown. It's as Captain Rose that he meets an unusual young woman -- one who threatens all his plans.

Read an excerpt of this book here.

"Known for her marvelous storytelling, Beverley sets the finale of her Rakish trilogy in Georgian England. Amongst danger, secrets and retribution, she ably places her protagonists into the era. With a sharp eye for detail, dialogue and touches of humor, she incorporates a few characters from previous novels into the mix and keeps the reader well entertained in this captivating gem.
Summary: Four years ago Bella Barstowe was abducted and feared for her virtue. She was saved by the roguish Captain Rose, master of the Black Swan, but she fled, not knowing that Captain Rose was a cover for the powerful Duke of Ithorne.
Now living in London, she copies letters for a scandal sheet. When she uncovers the truth behind her kidnapping and vows revenge, she turns to the one person who can help her: Captain Rose. Thorn is happy to oblige, for he's never forgotten that intriguing female. Other problems put Bella in danger, and Thorn must use his rank as the duke to come to her rescue again." -- Joan Hammond, Romantic Times